Well the shirts an nickelis fell on top of glen
Well in the walking dead tell tale game, Kenny, one of the main characters gets stuck in a similar situation in savannah. Everyone assumed he was dead, with the thousands of walkers he fell into along with Ben, but however, in season 2 we found out he survived. So it is totally possible for glen to escape that situation. I think the guts must have spilled all over glen, making him blend in with the walkers like he did in season 1, allowing him to escape.
I have 5 proofs glen is alive
1) Intestines aren't located in the chest such as the ones being ripped apart, meaning it must have been from Nicholas's stomach on top of glen
2) You can clearly see how much higher the spot glen is being "eaten" is from rest of his body
3) He was just screaming, no tears, and wasn't even coughing out blood like everyone else that gets eaten
4) If you look closely at the end of that scene, it appears as glen slid right under the dumpster
5) A extremely familiar situation has happened in the video game in which the dude survived
What do you think?