From CARA's website:

"Eucharist and Belief in the Real Presence
Nine in ten weekly Mass attendees (91 percent) say they believe that Jesus Christ is really present in the Eucharist, compared to two-thirds of those who attend Mass less than weekly but at least once a month (65 percent), and four in ten of those attending Mass a few times a year or less (40 percent).  Among Catholics attending Mass at least once a month, the youngest generation of Catholics (born after 1981) has similar beliefs about the Eucharist as Pre-Vatican II Generation Catholics (born before 1943)."

So there are in fact Catholics who don't know about the Eucharist.