It is always a great risk in removing mylar - even though the rewards are great with a successful removal. I don't think there was anything "wrong" with you technique. Insert lift is "hit and miss" - very hard to predict. You might need to source a set of decals (if they are made) - and lay down fresh mylar like MartyJ did on his T2.
Don't stress too much - We have all been through this. I destroyed a 9/10 Playboy removing mylar.
