Nothing to indicate he committed any crime. It is generally not illegal to have legal firearms in your hotel room or in your luggage.
It sounds as if they are looking for something to hang an arrest on. Not unusual procedure for officers when they screw up.
The game is then to “drop the charges” in exchange for no lawsuit. It is hard to “drop the charges” if there are no charges to drop.
We can argue until we are blue in our faces whether it was a legal search—we don’t know and the article doesn’t tell us. But he committed a misdemeanor, and you can’t tapdance your way around it.