Pro Sites payment when different email address is used

It would be helpful if the site name was included with the PayPal payment profile.

The following has happened to me a few times now where I will receive a payment but I can't find out which site to connect the payment to because the customer name and email used for paypal does not match the user name and email as registered for the Pro Site. The system knows (I assume) but I also need to track payments as well.

I noticed the PayPal payment profile includes an invoice number - where is this number generated from? Is it something I could track back to the pro site?