Hi MeatWadMan,
Welcome to the Apple Support Communities!
I know how frustrating it is when a file cannot be played from iTunes. There are a few different things you can do to get this resolved though. When you click on a file in iTunes, it reads and plays that file from the iTunes Media folder on your computer. Most of the time when you receive an alert like the one you are getting, it is because that file is not in the iTunes media folder. The first article attached is the one that explains where the iTunes Media folder is located and how to move a file into it. Please read over it and use it as a reference.
Where are my iTunes files located?
http://support.apple.com/kb/HT1391
I gave you that article first because it sounds like you know where the file is located, but it just may not be in the correct spot. If you cannot locate the file, please use this attached article for help locating it.
iTunes: Finding lost media and downloads
http://support.apple.com/kb/TS1408
Have a great day and please tell Master Shake and Frylock to do so as well,
Joe