Other FTers have indicated Emirates is notorious for only releasing one F award early in the reservation window, and then unpredictably releasing more inventory, sometimes nothing more until sometime within the T-30 window, and sometimes not until departure date. It is not unreasonable to assume the Skywards award seats were either grabbed by another px or EK sold a rev tkt(s) thereby indicating a bump in demand and the inventory got pulled. It's striking to me though, that you can find inventory (albeit at a very high redemption rate) via aeroplan at this juncture. Good luck!