I, too, have JUST had this problem: supposedly for leaving too many matches early. I will admit, I have, mostly due to connection on my end that makes my in-game self "stutter" for one day. Knocked from like Prestige 1, level 12 or so, all the way back, challenges reset and everything.
Well, it said I was on "probation", however that works, but now all my stats got reset... Seems rather disproportionate to me.
Edited the title and will lock this thread.
Forum Usage 101 - Search before you post.
A standard forum search for "deranked" and filtered by "date" would have helped you solved your issue.
Here's a [Link] to the search page.
The second thread would have answered your concerns.
I'll paste it here though. - You contact Cutpurse on our board, a developer, to have your case investigated. Include that you've been deranked and the likes.
The link will take you to a PM page already populated with the username.