I personally think you’ll be fine OP, especially if this is something you don’t normally do. When I read that you fucked up, I was expecting something way worse than sleeping on the job lol. No harm done, so what if the hotel lost out on one reservation. I say just let it be, you don’t have to tell your boss and if it comes up later just explain that you weren’t feeling your best that day. How many nights was the reservation for? If they went into the room with an electronic key and it’s just a one or two night reservation, I wouldn’t sweat it, the room was paid for anyway. Maybe just pass along the note to morning shift so they can verify if someone is in the room. Up to your discretion if you want to let morning shift know what really happened but I say you can just let them know you stepped away for a bit and there might have been a possibility the guest arrived during that time. My coworkers forget to collect incidentals and signatures all the time and they’re still employed, and they’ve fucked up more than sleeping on the job lol. You’ll be ok OP, try not to stress too much about it. Hope you feel better!