Nerites will get themselves into the tiniest spaces. I once needed to treat for whitespot (before I found out about the heat method) and just about all whitespot treatments kill snails. I found all but one nerite and I even took every piece of decor out of the tank and examined it. It had to take its chance with the medication. A couple of days later I found it crawling up the tank wall.
I have a long, thin wire stick which I use to flip nerites back the right way up. Sometimes I just can't flip them over so I push them against the tank wall or some decor then they have something to get hold of.
Snails get themselves into the funniest situations...I think I will also get a rod-shaped object of my ownHere's one of my goofballs, on the underside of the lid (lid is open)...I forget they do this, and sometimes when I open the lid, they fall back into the tank, but land upside down...I just use a bent wire coat-hanger to right them