Galena
I have an objection to you leaving him at your West Seattle house, and this is why: a cat’s directional sense is probably much better than their short-term memory. I think that your cat left the LA house because it was unfamiliar, possibly even looking for you – and then couldn’t remember the way ‘home’ because he didn’t remember that his family was staying at a new ‘home.’ It should be evident from the way he ‘hung out’ with you when you got to that house that he misses you and would be far better off with you. Cash in your plane ticket home (if you’ve got one) and catch a Craigslist or RideJoy ride home for cheap. When you get there, keep your cat in the home for many weeks, until you’re sure that he has set up habits and explored every corner. Only then walk him outside, on a leash, to explore the environs. Take him outside that way many times, and then try staying outside with him for brief periods without the leash. If you do all that, I doubt he’ll go back to West Seattle.