Help with my hermit crab!?

I had 2 land hermit and 1 of them died from stress i think. The other one has dug under a piece of driftwood. I do not want to disturb him because i don't want to stress him too. I've had the other one for about a month now. He doesn't come up for food or water. I don't want him to die. My tank is huge and beautiful full of many things to do i have climbing plants and vines fresh and salt water. Humidity and temperature is good. I know need to buy more hermit crab but its hard to living in the m because hermit don't flourish here and i try to save them from the pet store this is my goal. So far i feel like i'm doing a bad job because i got only 2 and 1 of them died =( and during winter i can't find any hermit at Petco. Where can i buy hermit around this time besides the internet and is my other hermit crab going to be okay by himself when will he start to come out and eat. I know for a fact he's not molting. Please help and serious answers only. It would help if you have experience with land hermit . Mine is purple pincher.