I actually already spoke with them about that. I got rear ended about the same time I ordered the diff and unfortunately the same day I had to drop the car off at the body shop is the same day the diff showed up. It looked like just a bumper and taillight but they found some other stuff once they got it apart and had to order more parts so it's going to take another week. I'm pulling it out myself and promised to have it in the mail as soon as I get the car back but I'm stuck right now.
Oh dang that sucks. As long as you're in communication with them I'm sure its fine. But I do have a couple people who can't get their units built until more cores come back.