Did that when my videos got blocked. I knew I could go to court, but that never happens, and most videos get reinstated. However, in my case, YouTube just plain told me that "We've reviewed your claim, and it doesn't seem you have the necessary rights to this video, and your claim has been denied", and that was fucking bullshit. YouTube has no right to "review" my claim and deny it. They are legally obliged to forward it to the other party and stay out of the matter. They can't make a decision on the matter. But since they have absolutely no customer support, I wasn't able to contact them.