Yeah, but let's stipulate Nick was on top of Glen.
do you think the zombies would have just skittered off immediately after eating Nick?
Sooner or later, Glen is going to have to move. OR sooner or later he's going to fall asleep, and die after the first snore.
I know people have covered up in zombie guts as camouflage, but he is still going to have to do that in full sight and sound range of dozens of walker in the area he could reach by spitting.
There are tons of them on both sides of the fence.
Even if the others who were with him, all of whom are dead, or miles away with a herd behind him could get to him, there is no way they would distract them all of of him before they finally found him.
No fucking way Glen is alive