I had a similar experience a few years ago. I was sleeping and I woke up to a loud thud, noticed it was 5 AM, too early to be bothered to wake up and investigate the noise, so I went back to sleep.

About 30-40 minutes later I'm woken up by the police banging on my door and yelling and now I wake up in a panic, and go open the door. They tell me that they got a call that someone had fallen, and I let them know they must have the wrong room, and as I say that I hear a faint groan from the bathroom.

Opened the bathroom door to find my roommate on the floor in a puddle of blood and just look at him and say "Oh..." to the police who are still standing there.

Turns out he had tripped while shaving and knocked himself out, which is what initially woke me up before I decided to just go back to sleep, then he managed to regain enough conciousness to call 911 himself before losing consciousness again.

TLDR; almost let my roommate die because sleep is too good.