IT WASN'T the game, of course, that brought 31,000 baseball fans to RFK Stadium Monday night. It was the prospect of an evening of fun, nostalgia and tribute to 63 of America's folk heroes. The enthusiasm of the crowd and the byplay of the teams more than made up for the stifling heat. The chance to see Joe DiMaggio, Hank Aaron, Roger Maris--the giants of the diamond of the summer game--brought out fans hours before game time, just to watch batting practice and jostle for autographs.

As sports columnist Tom Boswell has related, the players had a ball. Some of the younger retirees met their own childhood heroes--Feller, Henrich, Schoendienst--for the first time in the locker room. Others enjoyed reunions, and all must have loved the rousing ovations that greeted each introduction. The early favorite with the crowd was 76-year-old Luke Appling, who hit a homer in last year's game. The former White Sox shortstop was declared the MVP of that contest, and at once sat in his trophy: a wooden rocking chair.

For those in the boxes and bleachers it was a chance to relive some mellow days, to cheer the favorites again and to impress their kids with bits of lore. When an old hero bobbled a ball or just missed a dramatic nab at the left field fence, it was quickly forgotten. A routine double play was cause for an ovation and a line drive single brought cheers. Homers by Al Kaline and Brooks Robinson delighted everyone in the stands by demonstrating that it is possible to hang on to the right stuff into middle age and beyond.

As for those under 15 who have grown up in this city without a baseball team of its own, Monday night was a rare treat. The real fans among them knew every name on the roster, if only from baseball card collections. Some never took off fielder's gloves, waiting for an errant fly ball. Many wore Yankee, Red Sox or Cubs caps upholding the loyalties of parents who grew up in more favored cities. It's especially sad for these youngsters that this city has a beautiful stadium with a Metro stop at the door, and many thousands of fans of all ages, but no team. Bring back baseball!