That's right. I have at least 6 new ones. They're extremely tiny, otherwise, I'd include a picture. My water is within normal parameters--not even close to being brackish. I don't have any other snails but olive nerites in my tank either.
They may have hatched for some reason but will die as well. Look at amano shrimp, they will hatch in freshwater and you can see the zoa's in the water, but they have to be moved to saltwater quickly after hatching or they won't make it.