You all may be correct. I don't know and I don't know if there will ever be a full answer.
The stamping that was wiped out appears to be V09DZ - they did not have the day in there. I believe the grind out would technically be called a repair, and would not be handled in the same general engine assembly area. Could possibly have been messed up on Monday - second day of the month, then fixed on Wednesday - the fourth day of the month.
Do we have anyone that worked in the Flint engine plant that might know how things like this were handled? Tonawanda might not be the same otherwise we could ask bergie.