If clearance was excessive, possibly. The rocker stud was tight? Each side has a guide as well, though I've not seen one fail. Every once in a while these will drop a valve seat. So it would be possible that it did so momentarily and reset itself.

ethanol fuel can leave a residue on valve stems and the valve does not close or does not close as quickly as it should. This allows valve clearance to increase momentarily as the engine rotates and the push rod falls out of position. This usually occurs when the engine has not been used for a while.