There were no signs of parachutes near the wreckage and the pilots may not have used their ejection seats, according to information provided by the prime minister.
Methinks that if they'd used their ejection seats, the Turkish Navy would not still be looking for them. Or, the Syrians would have already found them and much bruhaha would have already ensued.
If this was in fact a low level mission (100 feet or 100 meters MSL as suggested above) and a missile hit them, it might have been all over very quickly -- faster than a reaction to grab the face curtain/seat handle and eject.
Maybe, an ejection with unfavorable geometry ... lots of gruesome possiblities there.
RIP, gents (Capt. Gökhan Ertan and Lt. Hüseyin Aksoy).
Sorry to see you go. At least you died while doing what you loved to do: flying a Phantom. *salutes*