How many sids were there and how big was the tank? I think I might give it a try and get a few nerites and see if they leave them alone but still eat the smaller snails. From other forums that I've read after looking super deep it's usually that they eat any snails they see or don't eat any at all.I’ve not tried a snail that large but large ramshorns were a no go with my Sids. They are total little snail assassins lol! At least mine are but I’ve read of people keeping some they did not hunt snails.
They dive right into the shell so I’d be worried about any snail with them.
Even if the snail had a trapdoor, sids are fast little buggers. I’d also worry about antenna getting chomped.
But as with all things fish, it may work perfectly for you.