I have seen something similar to that.
2000 mustang customer said "The passenger rear tire keeps going flat"
Upon inspection I found a 1 3/4" spade head drill bit chuck side first through the tread andnout the side wall.
The crazy thing was the spade bit had been in there so long it was conformed to the shape of the tire, and worn down half way. God knows how long that bit was in that tire.