I found an unbroken egg in my front yard?

OK, so I was outside in my front yard and I found what seems to be an American Robin's egg. It was sitting there, all alone, not broken. I looked around for nests or near by birds, but there were none. So I left it there and went inside to tell my Mom. I looked around from my front door for a while, but nothing showed up. So I went to feeders supply and bought a heating pad and a little critter container. First I put a flashlight to the back of the egg to see if it was alive. It didn't look like it had started developing, but I incubated it anyway. It's now a week later and I've been checking on the egg. Just today I did the flashlight thing again and found a fetus/embryo and a bunch of veins, so I know It's alive. I called feeders supply to ask what to feed it and they gave me a number of a professional songbird specialist. I called her and she told me to buy chicken Gerber baby food. I plan to make sure the bird hatches properly and survives the first few days. The only thing I'm worried about is whether it will be able to fend for itself in the wild. What should I do when it has grown up? What if I try to release it, but it doesn't leave because it imprints on me and thinks I'm it's mother?