I have seen wheels come out of the bike box with bits of factory stuff in the tires/tubes. I've seen tubes with poorly done molding or seams, with what looked like poke holes in them right out of a tube box. I've also seen flats without any explanation. Show the shop this but do understand if they balk at warrantying the tube. You've done a lot of miles on it and also have taken it out of the tire already. Either of these can be a reason to deny a claim. But a tube is a small cost item and good customer relations is priceless. Let us know how it turns out. Andy.