That is an awkward situation. Is the PD (or whoever made the decision) aware that you are rotating there? The interview/reject decisions may have been made a little while ago, and if you just started then the rotation won't be on your transcript and you won't have any letters, so he may be unaware of the fact that you are currently rotating there. If not it may be worth reaching out to the PD and asking if they would reassess your application at the end of your rotation based on your performance there. If he says no or that your performance won't matter because your application didn't meet other standards then that's a bummer, but your best bet is probably just to stick out the rotation, do a good job, and do things like add extra research or rec letter that you can talk about at your other interviews.