It can be, so I have the question, what happens if I report one message and the thread will be deleted after my report?
What will happen to my report? Do mods will check before all reports and after they will lock/delete a thead? Does it stays unhandled? (I have around 30 unhandled reports)
If you report it, and its deleted after then it will be automatically handled, and marked as good. However, if a moderator chooses to deal with it manually before they delete the thread it could be marked bad. For example, if it wasn't accurate.
If its been locked or moved it will have to be manually dealt with. I tend to deal with it right away after moving the thread. But, other moderators might do it a different way.