What kismet! Fate!!
My lil' brother works at a GW. His store, and probably others, separates things out as they come in, and then ships them to a main warehouse for storage. They'll collect up a box of H'ween/winter coats/swimsuits, etc as they come in, and once the box is full they'll have it taken to the storage to be brought out when the season is right. They items stay with the store that way.
Perhaps someone separated your pieces, thinking one was more this season than that season. It's just fate that you walked in on the right day!