Is this theft or not?

Momma-bear

( this post is not pregnancy related) Ok so my s.o. went grocery shopping this weekend without me because I was with my mom for the day.. well when he does this he keeps the receipts for me so I can scan them. So I scanned it and went on about my day. Well due to this newly developed pregnancy insomnia I've been experiencing when it told me you earned cash back just a little while ago I clicked on it to see what items we earned cash back on... Then as I was scrolling I noticed a men's Halloween costume was "supposedly" purchased.

1: my s.o. and I do not celebrate Halloween

2: idk how this was a mistake by cashier when it is now the end of February.. there is no Halloween merchandise left nor has there been for months..

Is this like some new scam they do at big chain stores? What do you think happened?