I think you’re overthinking it. I used to go into the US often for business and I have never had any of my electronic devices searched. The best advice is to leave your phone at home and buy a cheaper pre-paid travel phone. Not because of privacy but what if it’s lost, stolen, or confiscated? It’s no big deal losing a burner phone.
This is the best idea. Just talk to them, best case they’ll help you with it, worst case is they’ll give you a talking to. Going around IT’s back is a very good way to get fired really quickly.