Praise be to Allaah.
Shaykh
‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) was asked this
question, and replied:
If
it is three days or less, then he should make up his prayers – by
analogy with one who sleeps. If it is more than that then he does not have
to make up his prayers – by analogy with one who is insane. And Allaah
knows best.