Whoever really wishes to know the only Church that Christ founded will, without doubt, be drawn to the Catholic Church, by an angel's hand if necessary. Those who die not knowing is because God foresaw their will and knew they would not accept His Grace. Most people really do not want to know the Truth since that would mean a total renouncement of sinful ways and a conscious act of responsibility towards God at all times.
"For the Lord searches all hearts, and understands all the thoughts of minds. If you seek Him, you shall find Him, but if you forsake Him, He will cast you off forever" (Chronicles 28:9).