1. I think it will be fine for a few days, as long as you made sure the fish were used to the water temp. We filter our tap water in a Pure before adding it to the fish tank. Or just buy a gallon of water at your local store.
2. I never really have had a sea snail, but i'm sure it just needed some fresh air or warmth, that is if you have it under a light. I wouldn't worry about it.
Good Luck! =)