I know I've never had a problem with returns at our Target. They've always been able to look up my receipts when I didn't have them, or if I did, it only took a few minutes. Actually, more like 2 minutes, since all they have to do is scan the receipt and that's it!
I would think that if some Targets aren't following the policy, then you should contact corporate. If they have the policy, stated on the receipt, then they should be following it!
And I could understand setting a 90 day limit no matter with a receipt or without. Like someone else said, that's a LONG time for clothing to change! Although that's why Carters is one of my favorite stores for my kids, they have no limit on return time. I've returned things over a year later, with the receipt, and no problems at all!