Nassalius and Turbo. It's been around 4 hours after addition and they havent moved an inch or came out from their shell. Maybe ill leave it for a day and do a sniff test as suggested .Are you sure it is dead, snails go through a stress phase as well, it can last a number of days depending on the type of snail. and there are a number of other things that could have caused your issue. Really the only way I know of to tell if a snail is dead (and I know there is someone who will correct me) is to pluck it out of the water after a day or so, and give it a whiff... if it smells like the unholiest death that you have ever smelt... it is dead... otherwise it is alive.
How was the salinity of the water the snail was in, and your water (come to think of it what is the salinity of your water?).
Also what temperature are you keeping your water?
What did you use to increase your ammonia level?
LFS water , 1.026, mine was 1.025. Floated to temp acclimate 30mins followed by a 30minutes drip.
Water temp at 25C dosed Dr.Tim's ammonium chloride to raise ammonia level.