Don't freeze the chick but keep in a refrigerator until your ready to ship to the lab, then pack it 'cold packs' and ship it immediately, if your not taking it to the lab directly.
Best I can tell from your pic, it had a prolapse vent. What caused it I'm not sure but one thing that jumps out at me is your temp is way to high in the brooder. At 2 weeks the temp in the brooder should be around 80°F. for the warm spot and be at ambient temp at the opposite end of the brooder...