Should I say something?

I didn't show up to work on MET day. I figured they would take time out of my UPT. I checked my UPT balance and found out I still have all my UPT left, and my timecard showed I worked the full shift on the day I wasn't even there. Should I keep my mouth shut and get this FREE money? OR say something now just in case they catch the mistake later, and I get in trouble for not saying something?