I'd just got to thinking the other fish must have eaten it (and disposed of the bones) and started to put the bogwood back in the tank, when I noticed a red tail sticking out of a hole in the wood. I couldn't believe it - the loach had got into a hole literally as big as itself, and wedged itself in. Once i put it back in the water, it swam out of the hole, and down to join the rest of the group.
Since then, it's disappeared again, and I've gently lifted the same piece of wood, only to find it back in there. I know they like small holes and caves, but that was mad!