I don't have any hard data on flame scallops (a.k.a. file clams), but I think there is no mystery as to why they die in captivity. I'm virtually certain that the problem is that they are filter feeders with a fairly high metabolism that are unlikely to get enough to eat in a typical aquarium...especially in the really pristine almost sterile sorts of low nutrient conditions that most reefkeepers are striving for.
I have kept flame scallops several times with varying success. One lived for over a year. Others not so long. None of them grew at all, which suggests that they were not getting enough to eat. When they die, they don't just die overnight, in my experience...their mantles, and body tissues overall, start to shrink. They get weak, and their shells gape more than usual. and then eventually they die.
I strongly suspect that target feeding is not likely to be all that successful, since a lot of filter feeders like this can have their filtration apparatus (the gills in this case) sort of overwhelmed with too much food all at once. I suppose target feeding might help a bit, but I think animals like this probably need to be feeding more or less continuously (with more dilute food) for good health.
In my experience, flame scallops seem to be pretty hardy creatures. They just happen to be hard for most of us to feed adequately, and they starve to death.
If you had a continuous supply of planktonic algae available, and were OK with keeping your tank slightly cloudy with this most of the time, then my guess is that you could probably keep them really well. Bivalves can be pretty picky about what they choose to eat though (particles from the water column are captured by the gills pretty much indiscriminately I think, but pretty sophisticated sorting of captured particles takes place, and rejected particles are expelled as a strand of material referred to as pseudofeces), so it might be that some experimentation (or library research) would be necessary to find foods of the proper size and composition that they would accept.
The business of them disappearing into dark recesses normally has nothing to do with them getting stuck there. This is where they want to go. When it finds a place it likes a
flame scallop reaches out with its long foot and attaches itself with byssal threads, often lifting itself up off the bottom so it is attached to some sort of overhang. You can sometimes trick them into attaching (and staying) in a place where you can see them, but there is a good chance they will keep trying to hide in a dark spot.
These are lovely animals though. Someday I'd like to really keep them correctly, but I think this will not be in a reef tank.
every 5 min I got a call about something in her tank 
