I had filed T279809 and got a notification that I could no longer see it. When looking up the task page, I get this message:
Access Denied: Restricted Task
You do not have permission to view this object.
Users with the "Can View" capability:
Members of a particular project can take this action. (You can not see this object, so the name of this project is restricted.)
The owner of a task can always view and edit it.
I authored the task, so I'd think I'm the owner. After reading the error multiple times, I have deducted that the owner can only always view it if they have this "Can view" which I can only guess I don't. (a link to a glossary would be helpful) So I'd suggest adjusting the text to better clarify the situation as it just confused me. I'd suggest "The owner of a task can always view and edit it, provided they have the "Can View" capability." and something similar for the line about "members of a particular project", but I don't understand at all what that "members of a particular project" line even means.
It could be simplified even further by simply saying "This task can only be viewed by users with elevated permissions". That's way more clear I think.
The title for the task in question was "Wikimedia was temporarily unreachable". I can only speculate that somebody posted logs that include their IP on T279809 and the task was subsequently hidden from public view. Or somebody deleted the task without telling me. (but I don't know why that would happen)