Serial number retrieval from I tunes

Hi All,

I recently got my Macbook pro stolen. It's registered with I tunes and I can see it there in my account details. I tunes won't give me the number for some reason? (whoever has it can just look on the back)

I have the receipt from PC world (UK) but that doesn't have the serial number on it. Have phoned them but they're not helpfull.

Any ideas?