There's a thread on the official t-mobile forum about it here
"Ok guys, we're tracking this down for you. For the moment, we have been aware that an update was coming to the market and its applications. I'm guessing they required updates to the applications themselves (reason: I don't know yet) and those applications which were updated on-time are back in the Market."
I'll post more as I receive an official answer. - Will Admin, T-Mobile Forums
Sounds like a general update to the marketplace - hopefully over the next 24hours those removed apps will start to appear again.
Well, that barcode scanner app better!