If it were new parts, an answer would be a little more clear, but I have no idea what their policy on used parts might be.

Just curious, did you guys re-use the old pedals? Have you done anything to the pedals since? What was used to tighten the pedal down?

Edit: I don't think used=screwed is a fair statement- you get what you pay for. If someone asks for a used part because a new part is too costly, that's on them. If this does come to be the case, see if you can work out something halfway with the shop.