Lost my TerrainSplatmapCommon

I wrote a splatmap shader for terrain based off the standard unity source, but shortsightedly I did some modifications to the TerrainSplatmapCommon.cginc. I then closed the project, and now there is no TerrainSplatmapCommon.cginc anywhere in my projects' folder. I'm not sure exactly why it's gone or who ate it, but now I have a shader that can't be exported into any other project.

Strangely enough the shader still works just fine, I even did some modifications to it and it built itself without the common file. Which suggests that the modified cginc file is still stored somwhere.

Does anyone know what Unity does to shaders that could cause my file to go missing? Can I retrieve my modified TerrainSplatmapCommon.cginc somehow?