Caitlin, the same happened to me, I wouldn't bother with neg feedback. they made a mistake, canceled the order, and refunded you. mistakes happen I say let it go.
I agree. I never understood people who wanted to leave negative feedback when an order was cancelled before it shipped. They didn't have to worry about returning an item and they got their payment back in full (usually very quickly once the error was caught)
Where's the headache involved to leave negative feedback? Save that for severe issues where it's actually warranted