Never seen this problem before and its only happening on One Custom map

I last saved my map when i went to load it again everything is gone like gone the inspector tab only says, the player and spawned vehicle. all files of models and terrain gone. but when i go into the game files everything is their.????

Whats happened and how do i fix this. ive never seen anything like this ever?

ive done a deep cache clear and still the same just makes no sense. so unless i can fix this the map is ruined.