just talking from my experience here... but the haddoni i had seemed to settle in a lot easier with 2 clownfish hosting it right away.. maybe that would have helped in your case... no one can say for sure though..
mine attached the first day i put it in there, and didn't move for 6 months until i had to get rid of it... even then i couldn't get it to move so i sold it with the big rock it was attached too.
a quote from the rc thread..
"find a flat rock that can be positioned to form an under-sand inclined "ledge" from the bottom of the tank/container to the surface of the sand. I typically make the sand about 3" deep. This "ledge" rock must be securely wedged so that it will not move at all when the anemone exerts force against it."
That is EXACTLY how mine was set-up.. only i didn't do it intentionally.. lol.. it attached to the rock, then the foot slowly slid to the underside of the rock, and stayed put.