Hi Kermit,
My X recently told me that he had signed up for food stamps. I know that's definitely different from being homeless, but it was shocking to hear that this once very successful person was no longer able to even eat on his own. It's just unbelievable, isn't it? A good friend of mine recently experienced something similar to you, seeing her ex in a place that made it pretty apparent that he was homeless. I know that doesn't help, but strength in numbers maybe does? Like Laurie said, maybe this is it for him. One never knows.
Take care.