Ask HN: Restoring emails from a hacked Gmail account?

So my girlfriend's father's Gmail account was broken into by some enterprising young scammer. After going through the Gmail password recovery process, switching the language back to English, and emailing all his contacts an apology,(the scammer was trying to get his contacts to send Western Union money to "him" because he was stuck in "Scotland") I can't figure out how or if I can restore any of the emails that were deleted.

The scammer appears to have deleted his entire library of 6 years of emails.

Any help would be greatly appreciated.