Clown loaches typically take a few weeks to get acclimated to their new surroundings. They tend to hide for the first two weeks or so (I didn't see mine for about 3 weeks, except at night when they feel it's safer to come out). This doesn't necessarily mean anything is wrong, they just stress a little longer than most fish about being in a new place. This stress is completely normal, and shouldn't be taken as something you are doing wrong. Eventually, they will start to come out during the day.
I have similar "plastic" rocks in my tank for decor, and the clown loaches don't get stuck in them. In fact, clown loaches typically like hiding spots not much bigger than they are, but I have never seen one or heard of one get stuck in any rock or driftwood.
They may take a few days to a week or two to start eating (or at least, eat while being watched). Not to worry; they can go for days without eating.
Be sure you feed them something that will sink to the bottom of the tank in the beginning, so they don't have to venture to the top for food as they get used to the tank. I recommend TetraMin tablets (mine go nuts for them, plus they make cool sounds when eating them). I also use shrimp pellets, though they go after the tablets first in most cases and come back to clean up the pellets. After they are more comfortable, they won't be shy to come to the surface for flake food too, but continue to feed them sinking food so they get a variety.
Be patient, I assure you that clown loaches are worth the wait.
