Just create your 5 second empty wav file and then store it at a fixed path, and then Keyboard Maestro can use the Copy a File action to copy it to the specified location.
The same sort of technique as described:
can be used to iterate through the spread sheet file names and copy the empty file on the missing files.
Make sure you have good backups, and then you can use the fact that the Copy action will simply error if the file is already there, so just copy it unilaterally and configure it to ignore any errors (don't abort and don't notify) and you should end up with all the files matching the spread sheet.