I'm obviously not worthy of being in the company of the Gods on this forum, as I too have missed putting the gear up.
It was a long time ago, so the details and systems knowledge are no longer as clear as they once were. I do remember it was the first flight of the day after a min rest overnight, with a 0630 departure. Also that it was day four or five of multi sector days. I was PM, and as the captain called for gear up I got distracted by the master warning. I had forgotten to turn off the APU after start (we usually use ground power) and the APU wasn't certified for use in flight. So I cancelled the warning and shut down the APU, forgetting all about the gear. Fortunately I picked it up in the checklist.
As for the noise, compared to those props, it was nothing. The aircraft I'm on now has you to leaving the gear down after takeoff if there is a brake deactivated. For those couple of minutes we keep the speed to around 220/230 kts because it is LOUD!
Mistakes happen.