Well, some would say that bigfoot is "well documented." And I've seen videos of ghosts and UFOs....
I don't know what your father saw, but it was not an evaporated fish egg.
***CAUTION: SCIENCE LESSON***
When water evaporates, water MOLECULES go from the liquid state to the gas state. They can't take anything solid with them. The water becomes "dissolved" in the air in a sense. Next time you have some time to kill, take a dish of water out in the sun and spend a few hours staring at it as close as you care to. You will NEVER see even the tiniest drop of water come out of the dish. The water will be in the dish, then a while later it will be "gone." Any solid, like a fish egg or even the smallest speck of dust, will be left behind in the dish.
Where's Cephkiller? I know he'll back me up on this one.
***END SCIENCE LESSON***
Coming back to the original question, I'm willing to bet someone stocked the pond. It could have been the developer. Or it could have been someone else in town who saw this as a potential new fishing spot and decided to take matters into his own hands and brought a few bass from somewhere else. I know a guy who likes to do this. It can create some pretty good fishing during the few years while a subdivision is going up (or until the secret gets out).
There are a lot of subdivisions in my town built around a pond. But there's one subdivision in particular that's not very old but the pond holds some huge fish. I know a guy who caught a 29" striper out of there. IMPOSSIBLE you say!?! Well, it turns out that this particular "pond" is not a retention pond built for the subdivision. The subdivision was actually build around a flooded quarry pit. It's supposedly as much as 50 ft deep. It's the best kept secret in town, so don't tell anybody.