Looking back, the feeling of being 'trapped' was somewhat reminiscent of my experience of 'sleep paralysis' (and also occurred as I was falling asleep) though on an ineffably more terrifying scale. I'm not sure if other people who've experienced bad trips on weed (that are hallucinogenic in nature) have felt something similar.
When I awoke the next day, I suddenly had the distinct realization that the existence of other living beings and their eventual death (as my own) was an immense gift. Eternal existence as some monistic 'God' suddenly appeared to be the ultimate hell.