thanks, the system has auto-deleted the topic and the reason is said to be “deleted by user”. perhaps it’s the first reason that the topic has got locked.
but how does it work? previously users didn’t have the privilege to delete their topics and they had to inform admins to do so.
By default, users can edit (or delete) their topic only during the 24h after posting it (see setting post edit time limit.
It is possible that when a user deletes its own topic, the system automatically closes it.
And by default, deleted topics are completely removed from the topic list after 24 hours (see setting delete removed posts after).