Shouldn't be difficult to use, just ask if you're unsure.
The data you're referring to would be kept in the xenproduct_transaction_log table with a transaction_type of 'cancel'.
There is an issue with carts being deleted, but for some reason this was crossed off my to do list -- carts should be set to "inactive" but I don't think this happens. If you can log a bug report at XenResources.com that'd be appreciated.
Incidentally, you can at least track the transaction back to a specific user via the transaction_details field in the transaction log table. Once you know the user you may be able to take action that way. You can also check the xenproduct_download table - if there's no record of the user in there then they didn't download the product (and therefore you wouldn't have their license URL anyway).
Stay tuned for XPM 1.3 because there will be some changes focused on improved logging which should make cases like this easier to investigate from the front end.