Likely you've already been to a vet, but there is a way to get a large egg like that out. Here's how:
First, you do as you do the palpation: glove your hands, lubricate your finger with olive oil or KY jelly (my preference as it washes out).
Insert your right hand index finger into the upper part of the vent - against the top wall of the cloaca very gently. Use your left hand very delicately against the abdoment to very very gently "sandwich" the egg between your finger and hand to guide it back and out of the vent. Oil the egg within so that it will come out easier.
If the egg is too large to pass, you can poke a hole in the part of the egg that it out of the vent (the end) and collapse the egg slightly so that it can more easily come out of the vent. It is *** absolutely essential*** that you do the following step immediately afterwards: Use a baby's ear syringe or a baster from the kitchen to flush the cloaca over and over inside with *cool*, not warm, water. If you have it, use a few drops of Nolvasan in the water. If you don't, cool water will work. This flushes out the bits of egg that you couldn't get out, cools the tissues to reduce inflammation and reduce the chances of prolapse. It's as important to get as much of the yolk/egg white out, too.
In these cases, it's helpful to have penicillin injectable onhand and know how to use it to prevent infection if there were any cuts.
In the mean time, I hope the vet visit went well. Perhaps he can give you some oral penicillin or amoxicilling to help with the wounds, etc.
Please let us know how it goes, and honsetly if I were you I'd still keep the thread here.