i dont know what kind sandbed you have but you most likely don't wanna go mucking it too much, but if it were me, after this long I would start looking for him. This only holds true if it was a smaller type tank, I don't know if i would ripping my 125g tank apart looking for a fish. LOL Not that i wouldnt think about it.
I also would be on guard with that sand sifting star. they eat from the sandbed and if they run out of food they will dig down and die under the sand.
I'd still try to find him though, at least give it a go. he may be hiding so well you've missed him. Or you could find him at least then you won't have a spike.
let me know how it turns out. I'm hoping he's just being elusive! Good luck
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.