Shaun, make sure that there is not a red box at the top left of your screen. If there is then anything you are working on is not saved. Saved work occurs as you work on things and if you are not currently connected then it cannot save whatever you are working on.
However, assuming that you are connected:
Map items and character tokens should not vanish if they were there. However, as Quatar said, sometimes another object on that layer will cover them up.
This should not occur either but it is more likely.
If none of this helps, let us know.
- Gauss
You two called it. However, I was working on the correct layer (map layer) and when I switched to another encounter page and came back it had shifted the objects in the map layer. For example, it put my trees, rocks, and horse drawn cart underneath the grassy field. I will check in the bugs and glitches section to see if this has been addressed. Thanks for the idea Gauss and Quatar.