They did the farewell tawaaf and travelled on the 11th, and delegated someone to stone the Jamaraat on their behalf on the 12th

If the situation is as described, their Hajj is valid but it is lacking to the extent that they missed out by departing before staying overnight in Mina on the night before the 12^th, stoning the three Jamaraat after the sun passed the meridian on that day and bidding farewell after that. Undoubtedly they sinned by doing what they did, which goes against the words of Allah (interpretation of the meaning): “And perform properly (i.e. all the ceremonies according to the ways of Prophet Muhammad صلى الله عليه وسلم), the Hajj and ‘Umrah (i.e. the pilgrimage to Makkah) for Allaah” [al-Baqarah 2:196] and the words of the Prophet (blessings and peace of Allah be upon him): “Learn from me your rituals (of Hajj).” They have to ask Allah for forgiveness and repent to Him from that. According to the correct scholarly opinion, each one of them has to offer a sacrifice of an animal that is acceptable as an udhiyah for not staying overnight, another animal for not stoning the Jamaraat, and a third for not doing tawaaf al-wadaa’, because they come under the ruling of one who did not stone the jamaraat, because they departed before doing so; and they come under the ruling of one who did not do the farewell tawaaf, because they did their farewell tawaaf before completing their rituals. 

And Allah is the source of strength; may Allah send blessings and peace upon our Prophet Muhammad and his family and Companions. End quote. 

Standing Committee for Academic Research and Issuing Fatwas. 

Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan