Today i went to go and get a old build i made a few months ago and most of the build has randomly deleted itself from the workspace this has never happened to me? Most of the parts i used in the build were meshes but no unions?
Is it possible that it didnt save? I would check your auto saves file just to make sure
I had been in the place where the build was a few times and it had saved
Well was it mostly meshes? Depending on where you got them from that person could have been banned or decided to delete those meshes, I would still check auto saves tho, you might not be able to get the whole thing back but its better then starting from scratch
I open my auto save files and it only gives 1 file and thats from the game with the build in any other files take me to other projects which is weird But thanks for your help 
Try to go into the developer tab on the Roblox website, and then you can overwrite the current empty game with a version that has the build. You can go back many months, as far as I know.