I got my band on Wednesday. I had a scopolamine patch behind my ear until Thursday afternoon (for nausea due to the anesthesia). After I took it off, the pain medicine actually started making me vomit (tylenol w/ codiene).

I called my dr and he said to quit taking it so I did. Now I feel ok, but I did vomit a bunch yesterday... I read that vomitting right after band placement might cause slippage...

Should I worry that I might have caused this already?

If your surgeon knew you were vomiting and didn't worry about it, I'd thing you don't need to either. Bring it up with him at your first post op appointment.