i would leave him alone. an anemone that moves is an unhappy anomone. let him find a spot and settle again. it takes more than just a sting or 2 for an anemone to kill a coral, believe me mine moved for about a week untill he finally got a spot he liked. im by far an anemone pro, but i did read the forum about anemone's in anemone and clownfihs forum, i wouldnt stress him more by chasing it down, he will come out, he may be looking for more light, less light, more/less flow, or many other reasons.