Unless they pull something seriously crazy out of their asses, there's no way he made it out of that hoard. The sane thing to do is to realize Glenn is gone.
That was like watching private Mellish slowly get stabbed in Saving Private Ryan. You think during that fight as the tide slowly turns against him, "he'll make it out of that." Then you'll slowly come to the realization, "oh.. No.. I guess he won't make it out of that."
Ok they made it to obvious that Nicholas fell right on top of him. But it still seems pretty unlikely to crawl under the dumpster without one of those walkers at least scratching him