How do you know this? Did he palpate up the vent? Or did he feel a mass in the abdomen? If up the vent and he felt an egg, then an emergency dose of crushed Tums (not Rolaids) for calcium is one thing to do (I mix with plain yogurt to get them to eat it), plus, one of the best things you can do for an egg bound hen is give her a warm bath (The steam, though not too hot, in particular helps egg bound hens). Let her sit in the warm water for a little while if you can, lube up her vent with KY or simple veg oil-if you drip it on her vent, she will draw it in. Blow dry her *they seem to like that* and put her in a warm, dark place if she hasn't passed an egg yet.
If it is a mass in the abdomen, could be the eggs have dropped into the abdomen, which is considered internal laying or false laying (there is a slight difference in the two, but the result is the same). In that case, there is nothing that can really be done.