Absolutely nothing will come of it, it has already been factored in to their profits and losses with self service. Going back and returning it would be worse as they'd have to bin the items (potential contamination etc) and they'd have you on admitting to "theft".

So please don't stress. As someone else said donate to help those in tough times if you're still feeling guilty.

Story time: a couple of years back we were at Vic markets right before Chrissy and they loaded all our stuff onto a $750-$1k cheese wheel.

I was paying and my partner loaded up the bags in the chaos that is the markets this time of year.

I noticed a puzzled glance and they put out another cheese wheel with reflex.

Couple of mins later that look of confusion was bugging me so I checked the bags and yup, my partner had grabbed the whole wheel. We returned it and all parties involved had confused "wtf?" faces for a 5 second interaction.

(My partner may kill me for sharing this story as it's an embarrassing but hilarious brain fart that happens to all of us this time of year).

Edit: and if you're looking for a charity ~ Childs Play giving the gift of gaming/toys to sick kids.