Don't think I'll be able to help you with that, it could be uploaded by anyone.I'll open your question to other experts, maybe someone else has a better idea.
i am having difficulty finding the video, what is the exact title and if you have a link to it would be helpful
the best thing to do is once we have that information would be to file a claim with the sites DMCA complaints dept to have it removed as long as you have rights to the video
you can file a dcma complaint with the site which in most cases will reveal the information on who posted the video. but as i stated earlier i would need more information on locating the exact video so we can document that for the site.
You will need this information for anyone else to do investigative work on this as well. my next recommendation after filing the the dcma complaint is to contact a lawyer in your area.
if you can assist with getting the link i will be glad to help file the dcma complaint otherwise please rate the assistance i have provided.