I guess it depends. If you shoved him off your blanket, that would be understandable whether you were autistic or NT. People's property, especially their favorite objects, are understood to belong to them, to be inviolable. People have shot burglars who came into their houses looking to steal their things. What you did is something any human being might do. Not saying it was the best move ever, but it was definitely understandable.
Did the staff actually listen to you when you explained what had happened? This other person took your things--that was stealing.
Can you trust the staff to deal with it if someone else takes your stuff? If so, can you get instructions about how to report a theft and get your things back? If you can do that, and you can trust your staff to actually get your things back, then you wouldn't have to hit anyone. If you're still not sure, get them to practice with you; pretend a couple of times so you know how it goes.
If there are too few staff and too many clients, things like this can go unregulated and people can lose their stuff to others who want to take it, and then when you protest, you're the bad guy. Unfortunately if that's the way things are, then I can't give you any advice but to keep your most important objects with you all the time, to be prepared to lose most of them if someone decides to take them, and to decide just how much you are willing to fight back.
I don't know whether people taking other people's things is common where you live, or if this guy was just an anomaly and most people respect each others' property. It's my guess that most people around you probably aren't going to steal your stuff, just like you most likely don't try to steal theirs. But if staff won't protect you from it, you're going to have to take care of each other, if you can. Hey, look on the bright side; at least they didn't beat you up or anything like that. They just grabbed your stuff. That's easier to deal with than actual physical danger.