Maybe because he's in a bowl. Do you ever change out the water in the bowl (Like water changes)? If not, that could be your problem. The water conditions are usually poor when a snail won't come out like that. I would recommend moving him to a tank with a filter.
He started out in the big fish mansion 10 gallon tank, but he never came out. I thought it might have been because of stress because there are two african dwarf frogs, a betta, and two other snails, so the tank he is in just has a sunset platy and a ghost shrimp...
I have many nerites (assuming that's what you mean by "zebra snail"). Is he new? Sometimes they don't always poke out right away.
I had a nerite with ghost shrimp and he wouldn't move either. I watched him carefully and saw that the ghost shrimp were nipping at him! I had put a decent-sized pond snail in earlier and he had died; putting two and two together, I think the ghost shrimp ate the pond snail and were doing the same thing to poor Mr Snail (aptly named). I moved him to a different tank and he's been a happy snail ever since.
Things to consider:
1. Water quality, like Nikita said. Do you have a test kit?
2. Temperature. They're not as picky as some fish, but they prefer water above 70 at the least.
3. Tankmates. Watch his fellow inhabitants: do they seem interested in him? Swimming around him? Pecking at him? He may be hiding because they're trying to nip his antennae.
However, given the information in your profile, I'd bet it's due to water quality.
1. Your 2.5 gallon tank is pretty overstocked. Platies need at least 10 gallons (I have a few myself, they produce a lot of waste and get pretty darn big), and inca snails produce a lot of waste for a snail, too.
2. Your 2.5 gallon tank has only been set up for a few days, so it isn't cycled.
3. Your 2.5 gallon tank does not have a filter.
I see that you are not familiar with the nitrogen cycle. I urge you to click on the underlined text in my previous sentence and read up on it. Understanding its concepts is critical to keeping happy fish. Unfortunately with so many fish/inverts in such a small tank, with no filter, things are likely to go sound pretty quickly. I highly recommend you upgrade as soon as you can. The betta is happy in his 10 gallon tank, but if you could purchase another 10 gallon, and make sure both are heated, filtered, and cycled, then you would have some happy fish, and I bet the snail would come out.
I just took him out to put him in the big tank. but he didn't move. His trapdoor had deteriorated and he REEKED!!! Note to self: Never go to 6th and Clement, or they'll sell you two dead snails in a row!!!
I agree with kinezumi89 about the importance of knowing about the nitrogen cycle. It is also very important to test you water, because "you can't tell the quality of your water by looking at it". I learned that the hard way.