Not much of a surprise they sold out considering they had free shipping on any LEGO purchase no matter what it cost. The shipping is what makes buying the polybags so expensive online. I ordered just the brown ninja set this morning when I found out about the shipping special.
When I need to get a poly off TRU.com, I add whatever product it takes to kick in the free shipping, and make sure it is pickup in store. When I pick up the filler item in store, I return it. The poly still ends up shipping, for free.