Because Sophisticles hid and re-showed the answer. Due to a bug (?) with the approval system, if you don't have enough points to bypass moderation in the section, your post will require approval again if you reshow it.
If it's showing "answered 13 hours ago by whoever" on your post, it's most likely due to another bug with the site. Posts waiting for approval should be treated like hidden posts, so that's pretty weird.
I approved the answer, so it should be there now.
