LMecher,
I recommend offering food on a stick daily even if she does not take the food. Repetition and familiarity seem to be important (as with most animals). Be prepared to spend 15-20 minutest at feeding time (so wait until after dinner or at a time when you don't have to do something else). You don't need to wait until she is out though but use a regularly scheduled time. After she starts takeing food less time may be needed but why would you not continue to reserve the time to enjoy her
? Keep the food in
gentle movement and about an arm's length from the mantle (or presumed location of the mantle) and watch for arm movement behind or
between the rocks (arm tips often look like a brissle worms). It is easy to miss interest and give up if you don't know what to look for. Usually Neal and I both participate and look for changes and behavior patterns. Just because you don't see her does not mean she does not see you. I am quite convinced that briareus is far sighted and cannot focus close up. I believe SueNami was an extreme case (he could not see things closer than 8-10 inches) but with two more in the house I think this may be something inherent to the species (or at least the ones in the Keys).
Another thing you can try when you do see her out is to drop a largish fiddler (mithrax don't work as well) directly in front of where you see her disappear when you approach.
You are lucky to have a young animal but, as I have mentioned, they seem to have to reach a certain age before they shed fear. I noticed this even in my mercatoris that I raised from new hatch and is likely a biologic selfdefense. Each animal is, however, different and has its own quirks (dare I use the word personallity?).
Something I have not tried but have seen some success with is denying food for a couple of days (ie wait until all the crabs are gone for a day or two). It may seem a bit cruel but establishing how the food arrives may be safer for animals that will live out their lives in captivity.
Not finding the carcass is not that unusual. They liquify the meat so all that is left is a brittle shell that becomes sand in no time and the gills and caraprice. Keep looking for the remains though as she will likely jet them out from the den area when she cleans up.