@tampalizard My advice is to put together all documentation you have of your loved one’s MI and always keep it available and updated. In a situation where the person leaves home or requires involuntary commitment, you can try to determine who/where the person would be evaluated and YOU can give them the documentation ahead of time, or at least at the time of evaluation if you are in the same location. I have done this when our son was wandering, living out of a car, in another state and I proactively made contact with psych hospital units in FIVE different counties where I thought he might show up. And that is exactly what happened. He was committed involuntarily ONLY because of the documentation of his history.
Since then, I obtained an emergency (now permanent) legal guardianship. He was/is an adult. Absolutely worth the money on many occasions since.
I also suggest making sure that your contact information is in his wallet, in his suitcase, or somewhere you can think of, in case he is found. If his ID already shows your address, that will help.
And as soon as possible after you have done these things, start researching the psychology of LEAP (Listen/Empathize/Agree/Partner) which you can read about in a book called I Am Not Sick; I Don’t Need Help by Dr. Xavier Amador (referenced in many places on this site). Our pleas to do (or not do) harmful things are unlikely to make any difference if the person is completely convinced that his ideas are real. Instead, using LEAP, you would say things like “I hear you say you want to go to ______. I hear you say you are concerned about _____. Is that right?” You may be surprised how listening and acknowledging what the person is saying (without agreeing with those thoughts) will get the person to change his attitude. Don’t we all want to be heard? I can’t explain it all here. You have to read the book. I have used it and it has definitely helped us.
You are cared about.