Save (.w3z) Editing

[OwOberon]

i was playing with my friend but he got disconected, i saved the just after he left but he can't see the game when i load the save (it has a free space)
is there any way to edit the save so he can join again?

 

[GhostWolf]

Surprisingly I can't find information about the file format online other than a suggestion it might be a text file. Can you upload it here? or open in a text editor and see what it shows.