There are a number of possibilities as to what may have become of Donald.
Apart from the obvious one of his having had an accident on the mountain, there is also the presence of the PKK (Kurdish Workers Party), who are internationally designated a terrorist organisation, and operate in the region. Apparently they are not averse to the odd abduction; but would they be found at nearly 15,000 feet?
The possibility of his having crossed the Iranian border and been arrested by the authorities there has also been mentioned.
The Turkish army also patrols the area and are suspicious of people like Donald.
Pictures of Ararat: