One potential reason that it can take some time to identify these guys is that a lot of gastropod taxonomy is based on shell morphology and not the actual body of the animal. So, it may seem like it should be really obvious, and it may be, but not necessarily because of the spotted body.
The "Hair" is called the periostracum. There are other species with this, but it still may be diagnostic.
Keep in mind though that some families of snails may feed on other mollusks, so snails and clams could be at risk.
It is also important to know this: that you saw it arrive on the Gulf View rock and/or have no Pacific rock in the tank.
If you would like, I know the malacologist at the museum here in Houston. I can forward that pic if you would like. From the side, it is difficult to tell, but I think it might be some sort of hairy triton, like
Cymatium parthenopeum parthenopeum
from:
http://www.gastropods.com/p/Shell_Cy...thenopeum.html
What do you think? (keeping in mind these are shells only, dry, and some are cleaned so the periostracum is gone).
Supposedly it is found in all tropical seas. But I am still doing so searching! Any chance for a shot from the top or bottom of the animal?