Unhelpful and uninterested manager

So I purchased a Nike 3 quarter shorts a little over a month ago in Totalsports bayside mall on a gift card I received as a gift. I love the shorts but unfortunately the stitching is starting to come loose. I can't for the life of me recall if I was originally give a slip, doubt it as I keep all my slips. So Saturday past I went in to exchange it. The staff were busy so I went to the manager who was sitting on a ladder on the floor, didn't acknowledge me until I actually walked up to him. He said he can't assist me without a slip and even thou I know more or less when I purchased it he was to busy to help me as it was month end and he doesn't have the time to go and look for a slip. I felt like I wasn't valued as a client and his whole attitude was uninterested. I am a regular client in this store and I miss the old manager and the old staff. Standards are slipping, so is customer service.