I am so mad about my BTA for the same reason. he settled in to a place in the middle of the tank kind of half hidden but half out so I was sorta ok with that
..he was there for a few weeks...THEN.... this am I get up and guess where he is...Fully open as beautiful as can be staring straight at the back of my tank !!! at least a good foot from where he's been. Now you can hardly see him.

Hopefully he'll change his mind and move again
I feed mine mysid shrimp and other fish food through a tube with a little bulb on the end that I just squeeze and it floats into his mouth. Kind of like a very long thin turkey baster.