Same issue here, clicking on Play in Steam on OSX throws an error “Failed to start game (missing executable)”.
When I open the app directory under ~/Library/Application Support/Steam/SteamApps/common I see two folders there: “res” and “Preorder Special Content” and one file “LICENSE.txt”. There’s no .app or unix executable
Removing the appcache folder and restarting Steam did not help.
Re-installing the game did not help.
Verifying the game files passes with flying colors.
The problem here is that your virus scanner(at least mine did) is detecting the Train Fever.exe as an infected file and deleting it. I would suggest disabling your virus scanner during the instal process. It will have to be a clean install from what I’ve experienced; i.e. deleting local files. Please let me know if it works!
Disclaimer: I am NOT responsible for anything that may go wrong with your machine during the process 😛