Best case scenario is he’s disappeared because he finally got help
I think that he's still out there, just indistinguishable from countless others with similar views because he changed his usernames and stopping doing art. Given that he's never liked the amount of work needed to produce a finished drawing, or the criticism he gets for it, or the attention of the trolls, I'm guessing that a therapist has strongly recommended that he just stop doing it. But I also think that there may be another factor: autistic tetrahydrobiopterin (BH4) deficiency due to cerebral folate deficiency. BH4 is necessary to synthesize serotonin, but also to synthesize dopamine. When your BH4 is low, your dopamine is low, which causes ADD. In particular, what I've noticed with progressive BH4 deficiency is that you gradually lose the ability to participate in hobbies that you love, but are just more demanding than what your newer, lower levels of concentration can handle. For example, I used to play Final Fantasy XI, a very complex, grind-heavy, unforgiving MMORPG, as well as high-"crunch" (rules complexity) tabletop RPGs like 3rd edition Dungeons and Dragons. But they both require a lot of mental energy and time investment, so as my dopamine dropped I played them less and less until I completely stopped. I still liked them, but I just couldn't get past the initial "hump" to get to the rewarding parts any more. I think this may have happened with Andrew and art.
To make things worse, if you have ADD they'll put you on stimulants like methylphenidate (Ritalin/Concerta) or amphetamine (Adderall); these increase dopamine release, but in the long term they'll deplete your dopamine levels even further since they aren't helping the core issue with dopamine synthesis (the missing enzyme cofactor BH4). Eventually you will reach a point of burnout where
no stimulant works any more. The cure is to supplement with BH4.
This works, I started seeing improvements within a couple of days.
Folinic acid can also help, since folate is necessary to recycle BH4 but self-antibodies against the cerebral folate transporter result in the brain having a hard time absorbing it; folinic acid is a form of folate that can be taken into the brain by a different method, bypassing the impaired folate transporter.