I assure you that they will price match. I spoke with a guy named Alex who said "it's good you checked with us because many of the store employees won't know...simply print your order confirmation, bring it into the store, and they should be able to adjust it so long as the sale is going on at the moment. If you have a problem, please call us back here at corporate and here is your case number that I have ready to go to our credit department should there be any problems with getting the price difference...."
So no receipt is needed, simply my order number, ID, and CC at most is what he said, though really they should just need the order number. Customer service and everything else will be operational that day. I 100% checked into it before getting my tv.