I don't know about everyone else but ever since the new patch I've had horrible problems with ceiling tiles disappearing. It's really frustrating, especially for builders and I would imagine for people who take screenshots for any other reason as well. I found a fix for it and I was so happy I thought I would share it.
Normally you would have to delete and replace the flooring from the floor above. This can be really annoying since you may have to move everything in the room to do it. Not anymore! Instead of trying to place a tile over the missing one, or trying to place all tiles, you need to place one tile but hold the mouse to drag it over the missing tile starting from an adjacent tile. If there are no ceiling tiles left in the room at all from which you can start dragging the tiles you will need to go to the floor above and delete at least two tiles so you will have one to drag the tiles from and one to drag them onto. I hope that makes sense. In that case you still have to delete a few floor tiles but it's much better than having to delete the entire floor! It's saving me a huge amount of time and annoyance and I hope it will help you as well. It does not work over ceiling tiles that were raised or lowered using cfe(at least in this build that I tested it in). I may be the last one to know about this but I thought I would share just in case.
Tips from the comments:
GokuKaren says "I also noticed that if you have MOO on and you go to color a ceiling and add a pattern, it will create a missing tile (some times). Additionally if you are using the hammer to delete something placed on a 2nd floor this can cause it too. I try to always use the hand to grab it and delete anything on the 2nd floor because of this. "
Aussie Karima reminds about the fact that after using cfe on ceiling tiles, you can use the leveling tool to pop the tiles back into the right level.