Five-year-old Jamie Heishman knew what happened before his mother put down the phone.

"He saw the expression on my face," said Jamie's mother, Chris Heishman, 28. "He said, 'Oh, oh, Mommy, is that Daddy?' Before I could say anything, he went running into the next room shouting, 'Daddy's laid off! Daddy's laid off!' "

Jamie was right. The rumors that had been circulating around his neat Carroll Heights neighborhood in this Western Maryland town had become reality. Fairchild Republic Co., a division of Fairchild Industries, would close its main aircraft plant in Hagerstown by the end of 1983.

Gary Heishman, 27, a $25,000-a-year metal finisher, who married Chris nearly 11 years ago, fathered two children and did much of the work on their $33,000 home, was losing his job. So were 999 other Fairchild employes.

Fairchild, the second largest employer in this already recession-bat- tered town of 34,000, announced Monday that it is closing its huge plant here because of the Boeing Co.'s decision to recall a $308 million subcontract for work on Boeing's 757 aircraft.

It was the latest in a series of economic blows to Hagerstown and surrounding Washington County, now reeling from a 12.3 percent unemployment rate, compared with a 7.2 percent statewide rate. Just recently, Mack Truck Co., the area's largest employer, laid off several hundred workers. Reagan adminstration budget cuts also have taken their toll, reducing public housing, mass transit and public works projects.

The ripple effect of recession has hit Chris Heishman as well as her husband. She was laid off three months ago from her job at Ormond's department store. "They told us this area was going to be bad for business," she said yesterday.

Across the state in Annapolis yesterday, Gov. Harry Hughes met with members of his cabinet to discuss the Fairchild layoffs and come up with strategies to alleviate unemployment throughout Western Maryland.

Among possibilities discussed, according to aides, was a special marketing effort to lure new industries that would use skills of those workers laid off and resorting to state capital projects such as road construction.

Despite its troubles, Hagerstown is keeping up appearances. Downtown may not be exciting by big city standards; but it's not as ugly either--certainly not as ugly as the boarded-up thoroughfares that mark recession ravaged cities such as Detroit.

Like Carroll Heights, many of the neighborhoods in this town of 35,000 are pristine places accented by well-kept lawns. But there are For Sale signs, even in the town's more exclusive sections, where such signs traditionally have been rare. And there is growing fear here that more For Sale signs will appear if the local economy does not improve.

Mayor Donald R. Frush, speaking of the Fairchild closing, said, "The immediate spinoff from this is going to be terrible. We're going to lose businesses that supplied Fairchild, and of course any time you lose 1,000 paychecks, that is going to hurt retailers and everyone else who has done business with those people."

Frush said Hagerstown proper already has a 14 percent unemployment rate, and that the extra job loss will not help, "but we're very hopeful that we can find new businesses. We're doing our best to sell our town and county and to attract new investors. I don't have the philosophy of gloom and doom. This is a very positive community. I know what we have done in the past, and I know what we can do in the future."

Meanwhile, the Heishmans say they don't know what to do. Both were reared in Hagerstown, and they want to stay and make their lives here.

"When I was in high school," says Gary Heishman, "I used to pass by Fairchild and say to myself that I was going to work there someday. I was on top of the world when I finally got a job there" in 1977.

But now Heishman said his family probably will have to move. Other Fairchild employes, including John Ambrosa, 53, of nearby Martinsburg, W.Va., are saying the same thing.

Ambrosa, an assembler who has worked intermittently at Fairchild since he was 17, says he has no choice. "You don't have to be a genius to see that there aren't many jobs around here," he said. "What else is there for me to do, but move?"

Fairchild assembler Elvy Golden, 23, says he plans to stay--at least for a while.

"I just got married this spring and just built a new house," Golden said, laughing. "My wife and I were talking about having a baby, but we could see the way things were going at the plant. So we decided not to have one, and it turns out to be one of the best decisions we've made."

Golden lives on a small farm in Hancock, 30 miles west of here. "I figure that we can hold out here through the winter. Our food bills aren't all that high," he said, about $30 a week. But he said that his twice weekly trips to the Valley Mall in Hagerstown will have to stop. "My wife and I used to spend all kinds of money there, going to movies and dinners and things like that. But there's no way that we're going to keep that up," he said.

Golden's mother, Alice, 58, who has worked at Fairchild since 1948 as an assembler, also will be laid off. "It's mostly because of my mother that I wasn't planning my life around Fairchild," Golden said. "She always told me not to put too much faith in big companies like that, because they could always pick up and move whenever they wanted to."

Heishman says he believes he has learned the same lesson. "From now on, I'm going to try to do whatever I have to do to make sure that this doesn't happen to me again," he said.

"The way I see it, I'm going to have to move in order to improve myself, in order to get the kind of job that I won't be able to get around here if I stay. I'm going to get as much training as possible. But I'm also going to remember that if you want to protect yourself against this kind of thing, it's not what you know but who you know that counts in this world."