If there was another planet it was possibly orbiting, that planet still would have been clearly visible by that point. You’d have seen the planet before you ever saw the “small moon”

And Han would have known if there was a moon or not because he looked at the charts before he jumped there. Plus any moon that WAS orbiting would have been destroyed when the planet blew up.

It just seemed funny to me that today was the first time I ever thought “hey, wait, of course it’s not a moon, there’s literally NOTHING FOR IT TO ORBIT out there.”