I have seen odd stuff. A guy crashed a nice light frame on the track, Head tube no longer parallel to the seat tube. Yank the fork, and no amount of persuasion got it to move, in frustration the mechanic pushed it even more out of alignment and Whang! with a noise like that even and resonance vibration afterward, it went back straight. I would not want to repeat that, but funny things happen. Had it been on a lesser bike, I would have suspected stresses built into the structure at work, who knows.