They both disappeared at the same time? How long have you had them? Have you looked at off hours like very early in the morning or late at night? Sometimes they go off light cycle for some reason.
The smaller of the 2 I saw 2 days ok then nothing they where eating like pigs mysis fish eggs all other fish fine besides 1 Bartlett anthesis I lost too tail rot a few days eairler but he was only fish with any signs of health issue
So these are new fish? They could be in the sand though it is odd that they were out and about and then decided to hide. Potter's wrasse are not easy fish to keep so despite the fact that they were eating, they could very well have "moved on".
I also don't think your Anthias had tail rot-- I think he had his tail bitten off in a dominance struggle with your other Anthias.
Don't give up hope they can stayed buried for weeks. Hopefully it was bullying so at some point hunger will over come their fear. Out of all my wrasses my Blue Star has the record almost three weeks.
fyi potters are one of the hardest one's. even though they may eat at first alot of times they just stop eating. plus if you have anything that may chase them they can and will hide for up to a week in the sand
They where eating aggressively I had one wrasse who would tail wip if they got close but not nip/chase they where out for 3 weeks eating not nibbles eating really well then disappear
Only thing I can think of is one morning I checked temp tank was 75 so I added a heater to keep it 78 -80
And now that I think of it I started adding vodka bout a week ago wonder if the didn't like that
I don't think a couple of degrees in temp or a slight fluctuation in alk from the vodka would effect them that much, corals would show signs first if they were eating well for three weeks. Unfortunately with them its a wait and see..hopefully it was just bullying and not a decease.