No, BTA's will post up under a rock, especially when adjusting to new lighting. It may saty there a day or two while acclimating itsself and it may leave its foot posted there for good. They like posting their foot under a rock/in a hole/in shaded area, so that if they need to retreat, they will not be in the open. This is normal and a sign of a healthy anem. Over the next few days, you will see him come out more and more. Prompting with food usually helps speed the process. Let it adjust and it will bloom out from under that rock for you, so long as it is healthy...any pics of its location, how its looking now, etc.
It is bleached and will need good feeding when it finally comes out. I personally like any meaty foods and I know I may get slammed for this, but I'm not a fan of silversides. I've heard that the bones can choke or tear the anem. I've also seen a lot of threads about a BTA excreting the bones and/or what's left of the food. This has never happened to me(as I've seen over the 12 months of owning BTA's) and anything fed stays in the anem.