After duplicating the chest and making dirty vertex colors (on the duplicate), when I went back to the original chest all the texture paint had disappeared. Nothing I tried would bring it back, even though the UV maps seemed to still exist and were painted. I did notice some of the maps had changed shape, I don't know how or when that happened, especially since I was only working on the duplicate. I'm going to start over from UV unwrapping step, but how do I avoid this happening again?
Did you save the image texture to your hard drive? It's very important you save your image texture.
yes, the files for both the brown parts and the metal parts are still on the hard drive.