Sounds like their position is law enforcement officer commanded the nurse to perform a medical procedure which as result of it being related to a border crossing was legal if there was “reasonable suspicion” which you have said the claimed to have based on your responses and lack of cell phone.

To be clear, not stating I agree with situation, fully understand law, your perspective, law enforcement perspective, etc — but claim that body cavity search requires a warrant once reasonable suspicion is established at a border crossing to my knowledge is inaccurate if you’re claiming it is.

Example of Google search that appears to return search results supporting this:

https://www.google.com/search?q=is+it+legal+for+us+customs+t...

Disputing reasonable cause is very hard to do. Most people would likely find it reasonable to be suspicious of a person lacking a cell phone. Also appears judge granted a warrant, which to me confirms they believed their the threshold for reasonable suspicion had been passed.