[Plugin: Contact Form 7] Uploaded file disappears from UPLOAD folder

Hi
I’m using the file upload option in the contact form and after a while – not sure how long – the uploaded file in the wpcf7_uploads folder just disappears..
ANy ideas why?
It gets uploaded ok and there are no error messages.
it all seems to work fine then the file goes!!!
Any ideas why?
Really appreciate the help as Im running a remix competition and people will be uploading their tracks very soon…
Cheers
Mat