This was interesting to me because I saw the Grateful Dead at this locale on quite a few occasions and they were pretty raucous and occasionally quite hallucinatory affairs. Would not be surprised if the person vanished behind the wall at one of their celebrated concerts, especially with the t-shirt. Or should I say, transmogrified?
Now this is admittedly pure conjecture on my part but there is no getting around it, there were a lot of people at that place that were often really high and I have seen a lot of wild stuff happen that is hard to explain rationally and which may have been occurring on a more astral or higher plane.
So work with me here, my bet is that the mummy was having a real good time at that ill fated moment when he or she met their fate. I probably knew them. I think dollars to disco hits, it happened at a dead show.
The way I see it, it went like this - they were spinning around in the lobby, heavily dosed, and somehow had willed themselves into the size of a molecule, antman style, at a peak moment during a spanking and acid washed China Cat Rider jam (through well known but top secret hippy mind meld techniques) and subsequently transported their newly shrunken crystallized being through a microscopic porthole to the other side of the plaster, having left the physical plane, now fated to spend eternity in who knows where, inextricably bound to Jerry's last fateful lick, gonna miss me when I'm gone.
We do comrade, we salute you, please wait for us on the other side. You paid a heavy price for the team.
I do wonder if the disappearance was noted in the parking lot. "Hey Bongwater scored a miracle ticket and never came back for his kind veggie burrito. Hmmm, maybe he moved to Oregon. Oh well."