The latest word on this highly sought-after but extremely elusive Frank Sinatra impersonator was reported by his current venue -- Casa di Amore restaurant on East Tropicana Ave. (702/433-4967), where he (usually) performs Monday-Thursday, 8 pm to midnight. All they tell us is that Bobby Barrett is "sick" and has "undergone surgery." There's been no word yet as to his condition or when he'll resume performances. In the meanwhile, to book Barrett for an upcoming event, call 702/568-9000.