Brigg fell out of tank!

Came home and found an adult brigg on the floor! I feed them, left for about 45 minutes and returned to find one of my snails on the floor. I can only assume that she was coming out to lay eggs. I immediately picked it up and put it back in the tank, however, her shell is cracked and missing a piece. Does anyone know if this snail will survive? She hasn't moved since I put her in the tank. Will her shell repair itself if she does survive? I'm hoping she does.

ok, took a picture.....she has yet to move. I thought I had every place covered on top of the tank. The only place exposed is directly in front of the filter, which has now been covered with a piece of plastic. There is no chance of this happening again. Please check the picture, I feel soooooo bad for it and fear it will not survive.

This breaks my heart. I've never had a snail fall out of the tank before & I knew it was always a possibility. I've taken the appropriate steps to make sure they couldn't get out, but obviously I didn't do enough. I know this looks real bad and I feel for it. I have put her inside a breeder net just to keep her away from the other briggs, there is no fish in their tank. I honestly don't know if it's worth the hassle of patching because she still has not moved. We'll see how she does overnight and then I'll decide in the morning. Thanks for your help.

I just checked on her again, still no movement and her exposed area is no longer black, it is white......what does that mean???

I think you're right
I looked at her when I got up, there was no movement - she is still in the same spot. I touched her and she retracted slightly but is not closed up. I think she's still alive but barely. I don't want her to suffer. What should I do? I don't think patching is an option.