I wonder how man people who are told to "feel inside the vent for an egg" are actually able to feel one. If an egg is inside the cloaca, it's a good bet you're going to see it pressing against the vent. By the time an egg reaches the vent, it's either going to come out on its own or it's "breached" and you have a major crisis on your hands trying to free it.
Most often, in my own experience anyway, the stuck egg is soft shelled or shell-less and it's hung up in the vicinity of the shell gland and the most important thing you can do is to give the hen a calcium tablet so that her contractions increase in strength to push the stubborn egg on out.
There are little minor clues that point to egg binding that don't include seeing or feeling the egg near the vent. One clue is the hen may be squatting in a nest or in the run or in a corner of the coop, behaving sickly and in pain. Another clue may be watery, yellow and mucous discharge, and sometimes a steady watery drip from the vent.
Another clue may be when you push gently against the vent, the hen will squat and push back against your hand. If you haven't seen cecal poops from the hen in a long while, this is a clue there's an obstruction. The hen may be panting due to the stress and pain.
There is always a chance these symptoms are from a bacterial infection. But if that's what's happening, the hen will likely be much more sleepy and quiet than an eggbound hen. In any case, it will do no harm whatsoever to treat for eggbinding anyway with the best thing you can do - give a calcium tablet to the hen whole directly into the beak.