If you synch the ipod touch, use the "transfer purchases" option, as if you buy them on a mobile device (ipod, iphone) then the license sits there initially, and you need to transfer both the license AND the song itself to your computer.
Itunes should give you the option by prompting you to transfer the purchases, just click "yes" and you should be all set.
Thank you so much it was really bugging me :D
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