Ah, a variation of the "No True Scotsman" fallacy at work. I couldn't have really been sincere and surrendered to Christ, because it didn't "take".
I'll leave it to the Christians on this board: Is the statement "I do not believe it is possible to be saved by the incantation of a few words or a brief, if fervent, prayer" Biblically accurate? Just curious...
So you prefer to believe that God is a liar?