Static Meshes Lost

Hello guys
Im currently trying to create a realtime arcvhiz project but encountered a problem in the process that i used to find alot in my previous projects.
After creating a new level of my existing project to add materials on the meshes,all of my static meshes were lost and the only thing that left behind was the white sphere that represents different static mesh groups. You will find attached a picture to help you understand my problem further.