It is definitely best to not dig up your salamanders. During warmer months, they will typically only stay "burrowed" for 1 - 2 days, and then come up to eat or for a dip in their water bowl. However, during winter months, they actually hibernate, and this hibernation should not be disturbed. My male Tiger Salamander would stay down for 3-4 months and my female would stay down for at least 4 months. The first year I had them, I was also very nervous that something had happened to them. But my vet assured me that this was normal behavior. Each year when March comes, I purchase crickets to have on hand for when they emerge. (Do not put the crickets in the terrarium, though, until your salamander is up, because they can bite your pet.) I also continue to do water changes.So don't worry -- salamanders love to eat, and they will surface when they want to eat.