Bypass File.Exists check for URLs such as steam:// urls with emulators

I have a basic program I wrote that forces Steam into big picture before launching a game. I added this program as an emulator but I can't use it as such because LaunchBox checks the rom path is an existing file before allowing it to pass onto the emulator.

A method to bypass this check for a given emulator or to simply skip it for URL formatted file paths (protocal://) would be very helpful.