It's a BJ ( it's practically the same scene as the 6), if I remember correctly it happen after Mia offers to give you one, after that the option is available for raise morale (during the morning).
My personal impression is that it was coded wrong and the order is inverted, I mean it should have been Mia offers you a BJ (5 scene, the one you're missing) then it should become a raise morale ( 6) because I remember I had the same issue.
To solve it I raised her stats to max ( affection), then it appeared as an option I think, I'm not super sure, my last playthrough was some time ago so I may misremember....
Depending on where you are in the story I can give you a save of mines so I can spare you the same effort.