This is why it is always good to stay in contact with other stores in the area.
There was a theft ring going on in my district years ago. There were 3 full price stores and 1 outlet in our area. People were stealing things from the outlet, returning them to full price stores and through a series of returns trying to obtain a receipt to eventually get cash for a return.
We didn't exactly have rigid return policies, but it was generally known that if someone wants to exchange something without a receipt, they don't get one once the exchange was done. The issue was the the receipt would only show the exchange, not if there was an actual receipt at the time of the exchange.
Long story short all of the managers had been communicating and thought something fishy was happening. I got a call one morning telling me that a woman was trying to return a whole bag of shit from the outlets that didn't have a receipt. Weird stuff too. Normally people might buy a few pairs of shoes, and one or two small things like shoe laces or a belt. This lady came in with a whole bag of belts, polish, laces and like 1 pair of shoes.
She said she had no proof of purchase and I told her it wouldn't be a problem, and I could just call the outlet where she purchased the items and have them look up her name and purchase info so I could do the return.
Needless to say, she put all of the stuff back in the bag and just left. It was nice working for this company because our higher ups would let us run our store. A few times I watched my manager take a pair of shoes someone was trying to return and told them to get out of the store before he called the cops, point blank. It was fucking awesome.