<human>: Can you summarize the given text in a few sentences?

I'm going to France next week, and I wanted to get some toiletries and a backpack. I went to the check stand with a $5 toiletry kit, a $5 bag of trail mix, and a $30 backpack. 

However, the checker forgot to ring in the backpack, even though it was sitting on the counter right there in plain sight. I didn't notice that I only paid $11 (sales tax included) instead of $43 (or whatever it should ave been) until I had left the store and got back in my car. The buzzer didn't ring her I walked out, and the receipt clearly says $11

With cameras everywhere, and a receipt that proves my guilt rather than innocence, am I in any legal trouble if I don't return the "stolen" backpack?
<bot>: The checker at Walmart forgot to scan an item, so I didn't pay for it and didn't notice. Am I in legal trouble if I don't return it?