If the file is not corrupted I would check following things:
1. Outliner, do you have any object in the outliner beside the cameras, if yes, mark the object in the outliner and then click "f" to focus on it
2. You might have hidden the object accidentally, try if unhiding helps
3. Activate under Windows/settings-preferences/preferences the autosave function, this will avoid substantial loss on the file you are working on, rescued me already several times