Current questions and answers regarding the map editor.

I think he did it in one map, but he created a separate AdvMapDesc for the dialogue, which could have been discarded if created in the usual way.
If so, there is a way to restore the map.
1. Create a new MOD using Resource.
2. Create a new AdvMapDesc, with the path and name matching what needs to be edited.
3. Go to /game folder/Mods/mod name/map path.
4. Copy the contents of the desired map there.
5. Resource -> Pack MOD
6. Resource -> Close MOD
7. Resource -> Unpack MOD
8. Select the created mod.
9. Open the map by double-clicking it.
10. Voila, you can edit it, save it, and pack it.
11. After you've done everything, copy it back from /game folder/Mods/mod name/map path to the map archive.