Yesterday, I wrote this answer, but then realized that the OP had considered breaking things into specific cases, so I deleted my answer. Right after I deleted my answer, I saw that the OP had accepted my answer. I undeleted my answer and commented to the OP, asking if they indeed found the answer useful. They said yes, so I left the answer.
I'm not so worried about the 15 points, but I am curious about why this happened and hope that it can be fixed so that others won't miss reputation they've earned.