Accidentally pressed uppercase K while reading a message in my inbox, then jumped to different folder to read other messages, then returned to inbox and the message I was originally reading is gone. An inbox search says the message is still there. So I went back to inbox but the message is still not visible. Searched again and this time tried moving the message from search results to inbox, went back to inbox and message is still not visible. Searched again and tried "move to inbox again". Now the message disappears from search results but still is not visible in inbox. Returned to search and now the message no longer shows up in any folder. I assume this is somehow related to thread management but is entirely non-intuitive and perhaps even a bug that I cannot seem to reverse whatever caused this single, non-threaded message to become invisible. Thunderbird 31.5.0 on windows 7 pro x64, if that makes a difference. Any help would be greatly appreciated.