The mayor of Hagerstown, Md., is missing.

Three weeks away from the mayoral election, Mayor Donald Frush told his staff to cancel his appointments and left town.

His whereabouts are unknown even to his personal secretary and his campaign manager. The white-haired mayor, 54, has not been seen at City Hall since Feb. 25.

"I'm sorry, the mayor isn't in the office and we're not sure when he's expected back," his secretary, Joy Schaeffer, told a caller yesterday. As to the exact reason for his absence, she said, "At this point we're all in the dark about it."

"It's like 'Where's the beef?' you know. They say, 'Where's the mayor?' " said LeRoy Metz, the somewhat exasperated chairman of the Frush for Mayor Committee. "It's pretty difficult to run a campaign without a candidate."

Metz said that Robert Nolte, a friend of the mayor's and fellow campaign member, knows where to find Frush and his wife, Nadine, but isn't telling.

The disappearance of the mayor, who worked as a management consultant before being elected to his first term four years ago, has been linked to a number of different causes. They range from surgery for an infected gum last Tuesday to the stress of the campaign against his Democratic challenger, Steve Sager.

His campaign committee issued a statement Friday saying that the gum infection, coupled with the campaign, had left Frush "near exhaustion."

Signs of that strain began to appear earlier last month. During testimony about a bond bill before a House committee in Annapolis Feb. 13, Frush started to describe his Korean War experiences. That night he called City Council candidate Larry Vaughn a "turkey" prior to interviews being conducted by the United Auto Workers, and he walked out on the UAW when he was told that he would have to wait his turn in the first-come, first-served sessions.

Frush later blamed the incident on fatigue.

"He gets sort of frustrated, and I know there has been a lot of pressure put on him," said campaign manager Metz. "He and this fellow Vaughn never did get along too well together."

As mayor, Frush is credited with encouraging the rejuvenation of downtown Hagerstown, a largely industrial city of about 35,000 in western Maryland. Until his disappearance, he was considered a favorite in the mayoral race against Sager, a former city employe who was fired by Frush two years ago and now owns a development firm.

Now Fred C. Burner, who is managing Sager's campaign, is trying to avoid the trap of overconfidence that may be inevitable in a campaign against an invisible foe. Still, he conceded, the mayor's disappearance "has created a bit of skepticism as far as people in town are concerned.

"We're going on as if everything was normal," he continued."He's still on the ballot."

That situation may change. The "Frush for Mayor" committee will meet today or tomorrow to decide whether to continue the struggle, Metz said.

"Something's really going to have to come to a head this week," he said. "We have a big campaign ahead of us." Metz said he had already had to cancel an interview with a local radio station, permitting Sager to go on the air unopposed. Frush is booked on several more radio shows, and has scheduled appearances before the League of Women Voters and the Chamber of Commerce before the March 26 election, Metz said.

Meanwhile, at City Hall, things are running smoothly without Frush, said Judith R. Chambers, Hagerstown's director of community relations, who artfully described Frush's disappearance as "an apparent extended leave of absence."

Chambers noted that the city had managed to survive mayor-less periods in the past. Two years ago, she said, Frush broke his knee in a hunting accident, was out for three weeks, "and we all managed to keep things going then."

In Hagerstown last night, people talked about their missing mayor with varying degrees of bewilderment and doubt.

At Laverne's Tavern downtown, Mary Heiberger said as she sipped ginger ale at the bar, "He sure is bringing us a lot of attention and I'm not sure it's the best kind. After this stunt, I don't think he'll be reelected."

But at the Cue N Cushion lounge on Rte. 50, Johnny Davis said he believes the whole story has been exaggerated.

"He's on vacation," Davis, a 26-year-old steelworker, said dismissingly. "There's a lot of stress involved in his job. He's an older guy. What's the big mystery?"