Me and a team of 5 have been working on an app game for about 2 months but out of no where our coder up and disappeared, its been close to like 5 months now and what we can manage on our own is no comparison to what he could do. Is there a way that we could run those files on the project editor and continue work from a build game file and data or are we just screwed
Well there is one way to acually get the sourcecode but its not pretty.
You could decompile the game dll file.
Look in your game folder: [gamename]_Data/Managed/
For these dlls:
Assembly-CSharp.dll → for c# scripts
Assembly-UnityScript → for js scripts
Open that file/files with a decomilation software like: dotPeek.
If you use dotPeek, select the dll, namespace or “root namespace”
right click a class and “decompile source”
Also use source control in the future if you care about your project 
Best of luck!
The script source code uaually can be restored without much problems except it has been manually obfuscated. A Unity build doesn’t compile to machine code as we use Mono. All your scripts are compiled to CIL code (common intermediate language). The best decompiler i know is ILSpy. It can view the classes in IL and can also decompile to C# or VB.NET.
Asset files can partially be restored but you never get back to the original files.
It also depends what kind of “build” you have. In standalong builds you can access the assemblies directly. An android apk file is actually just a zip file. So you can open it with most zip tools and extract the dlls. There are even solutions to “unpack” a webplayer build.