Anytime I've ordered snails online I have received them in just wet paper towels.
Now that I think about it, that is exactly how Indo Pacific Reef Farms shipped snails to me in the past, but then again, IPRF is located in Kona, Hawaii, which is a long hike from Ohio.
Premium Aquatics shipped the snails in large bags of water, just like you would ship fish. Trochus snails are a little larger than normal, but I think one of the reasons why they shipped them like that is because of the next day service they offer to SW Ohio. However, I was concerned with one bag of snails where most of the water leaked out of the bag...what little water remained in the bag was polluted by snail waste, etc. However, after 24 hours, all the snails appear fine.