Could be a cocoon or an egg case.
I think, as always, that the principle of “Occam’s Razor” applies.
If it looks like a rock, acts like a rock and there is no reason to think it is other than a rock, it probably is a rock.
Just because it hails from some unknown place of unknown origin and is an unusual event/object, leads no rational person to think it is other than a rock....
Glad to know that the astronomy folks have the tools to see it, track it and ponder about it. But come on, it is a dead rock from somewhere else. It won’t tell us anything we need to know. All we can do is scan it with various sensors and pretend to interpret something from the analysis.
It is a rock.
Can I get my Nobel prize in science now or do I have to wait?