Right now, the only way for people to know whether a character has been dropped or not is if they are no longer present at the camp.

If a character was dropped just before the time-warp to Hisui, it is possible for characters to ICly believe that are still in the normal time, though we OOCly know that everybody not native to the pokemon world was pulled to the past. Proper confirmation of dropped characters won't be possible until we return back to our normal time, at which point, you'd also find any pokemon they may have left behind in your PC.