I think you know your options, it's just hard to pull the trigger. This is assuming you've already talked with your partner about this and they are deliberately going against policy.
1) Go to your DM and report the entire situation and put everything on your partner as soon as possible. The obvious consequences being: You would be off the hook for any future punishment if it ever was found out, your partner would loathe you (not necessarily a bad thing or their right, but it would happen), you have proof that you do the right thing in case you happen to make any mistakes in the future.
2) Do nothing. This assumes you would go with the belief that it was your partner's mess-up and you believed they would fix it, therefore letting the matter go. This is fine unless you're a PIC. If anything does come out, you may not be able to shed all blame, however, so there is some risk involved.
3) Cover it up. The evidence has already been deleted out of the computer, why cry over spilled milk? Just know, nothing is ever deleted permanently and if the patient wanted to push it further you would both be reprimanded heavily for trying to hide the mess-up.
Personally, you might still talk to your partner and find out everything that is going on and ask what they intend to do. Your license isn't worth covering up their mistake and if you aren't satisfied with the answer then you should still go to the DM with it. If I had my QA deleted by someone else and I wasn't even told, I would be furious and I wouldn't give a single **** what they thought about me.