This does stink when it happens! I had a goldstripe maroon clownfish for about 4+ months just disappear. And cowboy572 lunar wrasses do not typically burrow in the sand atleast that i have heard of they tend to hide in the rock work so I would recommend checking your rocks i have had my lunar wrasse for alittle over a year now I got it when it was a baby and now it has its adult coloring but I once thought I lost mine but it turned out he was hiding in the rocks so check your rocks and hopefully you will find him.=)
29 gal temp lunar wrasse/ soon to be lps/sps nano
55 gal softy/lps reef