I just got fired for “stealing”

This lady called in and said she didn’t leave a tip that I put in. According to my former manager, this happens all the time, people call and lie about it to try to get the restaurant to reimburse the tips. But apparently my managers can’t find the receipt (I guess I lost it??) and couldn’t prove that she did, in fact, tip, so they fired me instead

I know for a fact she fucking tipped me because I remember being pissed about how low it was, $2 on a $50 check.

I’m kinda in shock and really upset right now. I just lost my job during this pandemic because someone lied and I was careless with my receipts.