Where have you gone, Vince DiMaggio—or whoever you are—has been the big question around Dallas ever since it turned out that the guy who hit town last spring saying he was Vince DiMaggio was not. He had a lot of scrapbooks and a good line, and persuaded Dallas financier Henry Helm to back a DiMaggio spaghetti house featuring "the same recipes we use at the family restaurant in San Francisco." But when the local press printed his picture "V�nce" was suddenly called out of town. Then Helm saw a shot of Joe and his brothers in a national magazine and got suspicious. One quick call to San Francisco and the real Vince DiMaggio stood up, "I want to get this guy off the street before he gives me a bad name," Vince said of the scrapbook-bearing sneak who had pulled the imposter trick before. O.K., but what happens to Helm and the spaghetti house on Lemmon Avenue? "You've got money invested," DiMaggio told him, "and if you feel like the name is everything, then leave it." And off he went to brief Helm's chef on those recipes they use in the family restaurant in San Francisco.