Pangea if he's got good feedback I wouldn't be too nervous yet. Give him a couple more days but continue to try to get ahold of him. Sometimes guys go out of town or whatnot. I've only been burned once on there but it was my fault, I bought outside the auction process and never recieved my item, they screwed me but it wasn't for too much.
Just DON'T leave feedback till you are satisfied, that's about the strongest lever you have, bad feedback is something most people with good feedback work to avoid.
ONce I bought a Nobler RC Plane at a garage sale for five bucks and sold it for about 150. It was a classic I guess.
I'd Like to hear more about that regulator, was it a collectible one or what? or did the Pawn shop guy sell a really nice one but didn't know what he had? Stories like that fascinate me.....