It does not look like a reflection (but anything is possible). It also could be a hair or something inside that move around when shipped? Unless it was on the outside of the lens (which I'm sure you checked)!?! I would be afraid of it shifting back.
If they will not replace the lens, then I'd ask for you money back and find a new dealer. If they send a new lens, I hope you wrote the serial number down so they don't send you the same lens.