Gun rights are generally not gone forever. Federal law bars people adjudicated mentally defective or formally committed to a mental institution, neither of which include a temporary mental hold for suicide watch. State laws vary, but none of them have a law where a single temporary hold means "gun rights gone forever." Some states let people go buy a gun the day they are released from suicide watch, despite how irresponsible that sounds.

The temporary can easily turn into an adjudicated one. Happened to one of my friends during a nasty divorce, the high-IQ husband knew all the buttons to press to the state and kept fabricating to the state that the suicidal ideation was ongoing (it never existed in the first place) and then they committed my friend based on that. He was then successful in getting my friend's ability to defend herself removed so that she would be defenseless.