I really think someone he knew must have picked him up. If he had just been wandering around for very long he would have been noticed, there'd be witnesses or video of that. People would have spoken to him if he was out and about with no place to go during tornado threat weather.
I am hoping he had a plan and ran off because he had a ride set up. I pray that is true. The reason I think that is because, even if one has neglectful parents or caretakers, there are sometimes older siblings, or aunts and uncles, that will step up when they get the chance, when a child is unhappy in CPS placement. I've seen it happen before and I pray that happened for him.
If not, I'm worried about where he could be now.