Here's my guess why he diseappeared: He hyped Kaiba as much as one could have and said that it won't fail no matter what. So he hid himself in fear of Kaiba being a failure, because he had a chance of humiliating himself as everything he had said will tear apart when it WILL fail.
I'm willing to bet that that faggot will come out again if Kaiba is successfull, but I doubt he'll come back again if it fails.
But it's not like anyone will miss him. Only newfags favoured him, I mean, the guy was present with his trip in /a/ for how long? 3-4 months top? He also caused and stirred lots of shitstorms and defended gurren lagann like a mindless idiot.
tl;dr nothing of value was lost.