1996 Subaru Legacy.

I have a brand new car battery. One week ago I drove this car for 60 miles. No problem. I went out of town for a week. After coming back when tried to start car, nothing. Not even clicks. AAA guy came. Jump would not work. He told me perhaps my starter is bad. Would starter go out like that? Wouldn’t I get some indication that starter is going? Other strange thing, when I opened my hood after it did not start, I saw that positive terminal on my battery was disconnected and battery tie-down was taken off. Seems like somebody tried to mess with my car but ran away, perhaps because somebody saw them. My question is, do you think it could be starter? Although positive terminal was disconnected, wire was still touching the terminal.