[Skryptec]

Nike is so damn easy to do a partial refund with.
I'll help you through this with a very basic, simple guide.

Basically purchase a few items from Nike.com all at once, so you get multiple items in the same package, just say that your shoes aren't in there... they'll start an investigation and end up refunding you for the shoes.
Or you could buy the same shoes from two different stores, just say for 1 store that you only got the left shoe so you want to return it and for the other store say you only got the right shoe.
You'll basically return 1 left shoe and 1 right shoe to both stores, you end up with 1 pair of shoes and a refund for both, maybe you don't even have to return it and they will just refund you or give you the missing shoe.

Boom, free pair of shoes and refund, 3 pair of shoes or 2 pair of shoes and refund for 1 pair.