If it happens again, try loosening the gas cap and see if you hear a slight hissing of air entering the tank. It is possible that the vent hose was routed between the tank mounting ears and the rubber mount when the dealer assembled the bike. This is a very common problem when the tank is removed, so be careful if you work on the bike yourself.

Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python