Ok, so here's the deal. You can make this as ugly as you want. At a minimum your BA can use this to keep someone else from being termed on an Article 52 violation (dishonesty). Your center management team has done something dishonest, so the BA has leverage.
The easiest and quietest way to resolve this would be to go to HR and ask nicely to have them chance it back. "It's too late" is incorrect. They can submit a prior period adjustment in Time&Labor.
The next is a grievance. Also, have a steward file a "request for documentation". You will need to ask for the "GTS Edit Log with Original and Changes" for the date in question.
Last would be a call to the Ethics Hotline. Depending on who actually changed it and how much you Division Manager hates them, it could easily get them fired.
The silly part is that this edit would really change the center stats very little. It the scenario you described you would still have scratched.
But why listen to me, I GotOut