Anyone know what typically happens with bonus MR on offers when an item is returned?

I have two items that were refunded. One was at Grubhub (the +1MR/$ offer) - the restaurant missed one of our dishes, so refunded. Then on Amazon (+5 MR/$), returned an item. In both cases, I see the original MR added in the summary, and then with the refunded amounts, I see the negative for the normal 1MR/$. However, I don't see any other transaction with bonuses clawed back - I see the original bonuses listed separately, for example, as 'Amazon +5 MR Pts Offer', but no other items that show negative of these for the portion returned. In both of these cases, it was partial refunds for the original charges.

I'm just wondering if I should expect these bonus MR to be clawed back (which is what I originally assumed would happen), and if so, how long this typically takes to occur.