At one point that question had been migrated over to SU, but I don't see it over there anymore so it must have been kicked back to SF at some point. I don't have 10K on SU so I can't see what it says over there.
I believe that my answer did have 10 upvotes at the point it was migrated to SU. Could it be that this badge was awarded retroactively?
After Ben Brocka's comment I noticed that all of the answers were deleted on June 1 which would explain why the badge was awarded. So now it looks like somehow the answers were undeleted and then redeleted.