That has happened and (I finished in July so I cannot speak to each and every event) they have all been hired by someone.
It happened to me, though I didn't fail the interview. I'm an "older" guy and there was some suspicion - evidently - that the younger FO's thought I might not be very good at taking instructions from a 24 yr old, so I was not offered a job. I am now going to PSA and think I am better for it.
Bottom line - Jet U gets you a job or they give you your money back. Even if you don't get hired, how can all that experience really be a waste of time?