What was his reason for paying by transfer?
I accept deposits by transfer, payment for movies or webcam shows, and I've also accepted it once when a client wanted to extend but didn't have any cash on him and didn't want to take time out to go to a cashpoint. I've never had a problem with it, but it's always been me who's offered the transfer method. I've never had a client ask for a booking and say they'd pay by transfer in preference to cash.