User "ABC" not found on CycleChat - seen at foot of messages

[Stonechat]

I often see at the foot of messages, e.g. If the message is from a user called ABC
User "ABC" not found on CycleChat

Clearly it is nonsense, but what is going on?

 

[Spinney]

https://www.cyclechat.net/threads/user-xxx-not-found-in-cyclechat.209603/