Actually, the status of your bitcoins is objective, but unknown. Something isn't stolen until you say it is, it's stolen when someone takes it without authority to do so or fails to return them, which is the case here. Whether or not you know or want to believe it is stolen is immaterial.

I believe that they are stolen, but I can't know for sure. However, the coins have one objective status (lost, stolen, temporarily unavailable due to incompetence). Nothing that you or I say or think about them will change that status until Ukyo does something with them, unless he sold/gambled/lost them, in which case their status is permanent.