Join Date: Sep 2012
Location: MDE
Programs: AA EP, CM PP, AV GM, UA Silver, SPG Gold, Hilton Diamond, Hyatt Plat, Marriott Plat, Accor Plat
Posts: 1,002
I have had UA destroy bags before, and their procedure is a nightmare on a good day. Policy is that it is the responsibility of the airport crew where the damage was discovered. I don't know what I would have done in your case, as you indicate that there was nobody there to whom you could report the damage.
Take photos. Document every detail. Prepare yourself for a lengthy and frustrating reimbursement process. My experience is that they will eventually compensate you fairly for your loss, but they won't make it one bit easy.
Wish I had better experience to share. Best of luck to you.