You joke about the music store "summer camps", but that could be a great opportunity if there are any in your area. That's similar to what I did at my local music store.

Who knows, maybe he went back to his band, told them about you, and they said something like "damn it man, would you STOP trying to recruit members...we don't need any more, I don't care if he's Eric Clapton!". Or maybe you'll hear back a month from now, like there's nothing odd that he's getting back to you in 2 months rather than 1 week. :-).