I've been told that this room is haunted, but I didn't really believe it until I heard a ping (while I was in the room and another), looked everywhere, but couldn't find its origin... This happened yesterday, and today there is still no sign of any ping in my notifications inbox, so am I dealing with a real ghost here, is this just a bug that I hear a ping when nobody has pinged me, or is there another explanation for this?
TL;DR:
I heard the ping sound, but I have checked, and I was not pinged, there is not other notification of the ping as there usually would be if I had been pinged, no sign of an edited or deleted message that pinged me, nor any notification later on in my notifications inbox. So where did the ping come from?