You can report what happened right here in the Forum. Right here in this thread.
You may also use a Customer Support ticket.
Or you may use the "Flag as Inappropriate" button/link available in the top right corner of the page on which you saw a job posting, or on a freelancer's profile page.
Have you tried following Preston's recommendation of flagging the job post? You can also send me a private message with more information about this case, and I will look into it further.