Tony - It happens to the best of us. If it is any consolation, I would have done the same thing. Better to just continue on with the rmoval, but start again from a different corner this time.
I've done countless mylar removals, and the most valuable playfield - Playboy - Is the only one I stuffed up. You DO "get over it". worst case scenario - Send it to Gavin !
Let us know how you go with the rest of the removal