?

I have what appears to be a cross threaded lug nut that I noticed after a full brake job. I went back to the same mechanic to have him fix it, but he claims that he didn't do it. He says that because the tire is off balance, the lug nut popped out from the tire. I pointed out that the treads on the stud aren't stripped as they should be if this were the case (leaving aside that this popping seems ridiculous). So he was going to charge me for the work. Rather than directly calling him a liar, I thought I'd check with some mechanics to see if such a thing could actually happen before cramming my foot in my mouth.

This is a '02 Hyundai elantra. The lug nut in question is 13/16 inch with what I assume is standard thread pitch.