update - i just spoke to MP and it was super painless. the agent was able to check the ticket immediately and see that it was booked in A, she credited the miles instantly on the phone, and now i am well on my way back to MVPG this year ^

i asked a few clarifying questions and she said that usually after a cash upgrade the segment would pull through with the original fare class no problem, and she had no explanation why it didn't in this case, since the other two segments on the ticket posted just fine.