If you spectate somebody for a longer time other spectators might sometimes just vanish from the list, though still being there and you can write with them at #spectator.
osu! version: 20140529.4 (latest)
osu! version: 20140529.4 (latest)
and was chatting in #spectator with Staiain, Asia Senpai and Fogsfles, and when he did a new map, out of these three, only Staiain was on the list, while still chatting with FogsFles and Asia Senpai in #spectator, while Staiain and I were not on their list (I heard)