I had similar thoughts. The egg was marked as collected 3/31, and she does collect daily since she has a larger flock. So it should have been less than a week old at set. It is possible there was a hairline crack I didn't see. It's also possible it was laid earlier, missed, and collected after somebroody sat on it a bit. I agree that just a few hours (not even a full day yet) in the heat of the incubator could not have caused that much rot so fast. It must have been a dud from the very outset. But, it's in the dumpster now. No telling what the cause truly was.