The OP states denied boarding, but most likely what happened was that the LX check-in agents refused to issue BP at the check-in counters because the OP had no Schengen visa.
Yes, I'm also surprised why the OP bough 2 separate awards for this itinerary. With Aeroplan there would be a big difference in miles/points between LAX-ZRH-IST and LAX-ZRH?