How u can strip the threads in the crank if you were using the bike? I mean, you take the pedals in and out daily or something? I have seen people putting the left pedal in the right crank and figure it out when the pedal was like 80 % in the crank, this way clearly the threads are strip and redone, but strip the threads just like magic w/o taking the pedal out and in the crank it is hard to do and even harder to believe, worse if it is the second time that happens.

If you can justify this probably the LBS will hear you. But sincerely i doubt they will believe it or buy it as Duck said.