Bulldozing restaurant lot deletes all staff

@DeenaHax Ok, to get your staff back, try this:

1. Take a look to the sims the game gives you as an option to hire. These sims will probably be sims you don't care about (you don't know them, your sims don't have a relationship with them) as the game probably just created them.
2. Go to Manage World, and then to Manage Households.
3. Delete the sims that the game gives you as an option to hire now and you don't mind losing (they will be unhoused, so keep that in mind to search more easily).
4. Find the sims that were your employees before, those you had already trained, and unhouse them (by your first post I understand you had them in a house). Also make sure they are not marked as "played"/"active".
5. Go back to your restaurant and try to hire them. If you don't get all your ex-employees as an option, you will have to repeat the deleting process.
6. Once you have hired all of them, put them in a house again to protect them.

Good luck!