Well, just as I was thinking I must have lost my last goby -- despite the absence of a body -- because relentless flashlight searches have revealed nothing. Then suddenly, while I was wondering of I should empty the tank and stop feeding it, I just saw him! He's mostly two black eyes and a black spot in the middle with a lot of body I can't really see, and at least a good 3/8" long and a lot wider through the head. He can definately eat BBS, so I will clean out the rots, start him on enriched BBS like the clowns, and give him a sponge filter, too.
I tried to scoop him up for a photo, but he darted away from zero to sixty in nothing flat -- just like a real goby! He is 29 days old today. I hope this means he made it through meta; heaven knows I can't see him well enough to tell.
Meanwhile, I still find it hard to believe I haven't lost in clowns since the first 3 days.