I'm not saying you do this (so don't take offense), but I'm sure there are people out there who might make a $500 purchase with a PCE 25% off (or CA 30% off coupon, and so on), pay $350 for their $500 worth of merchandise, and then turn around and return the stuff (which is NWT but conveniently no receipt) for $500 store credit. Of course, this is totally dishonest, and these people should be ashamed of themselves. I guarantee Coach flags suspicious returns for this reason, and even though you weren't doing this, Coach flagged the unusual activity.
I work in retail for a children's store and we see this all the time. We will have a promotion such as take 25% off your purchase of $75.00 or more. Someone will buy a ton of stuff and bring it back the next week without a receipt and say it was a gift. We will send them a merch. certificate in the mail and you bet during the next promotion they are in there spending the merch. certificate. Then the cycle happens all over again. There is one particular lady who I have caught on to that had a merch. cert for over a $1000.00 last week. When I first encountered her back in November it was only at $350.00. I think she realizes that I am on to her now but there is nothing I can do and unfortunately the company I work for doesn't really care either. I don't blame Coach one bit for being suspicious and getting their LP people involved. With this economy, companies are losing a TON more money due to LP issues.