Missing the standing at আরাফাত entirely means the হাজী has missed হজ্জ, as নবী করীম (সাল্লাল্লাহু আলাইহি ওয়া সাল্লাম) said: 'হজ্জ is আরাফাত.' If a হাজী fails to be present at আরাফাত at any point between the afternoon (zawal) of the 9th and dawn (fajr) of the 10th of Dhul-Hijjah, their হজ্জ is not valid and cannot be completed that year. This is the unanimous position of all four schools of jurisprudence.
Sheikh Ibn Baz explained the procedure for someone who has missed আরাফাত: the হাজী should convert their intention to উমরাহ, perform তাওয়াফ around the কাবা শরীফ and sa'i between Safa and Marwah, cut or shave their hair, and exit the state of ইহরাম. This converts their missed হজ্জ into an উমরাহ, which releases them from ইহরাম. If the হজ্জ they missed was their ওয়াজিব (first) হজ্জ, they must perform it the following year.
Sheikh Ibn Uthaymeen added that if the missed হজ্জ was a voluntary হজ্জ, there is no obligation to make it up. He also noted that a dam (sacrifice of a sheep) is required according to the Hanafi and Maliki schools for someone who missed হজ্জ and converted to উমরাহ, while the Shafi'i and Hanbali schools do not require a dam for the conversion itself. The key lesson is the absolute centrality of আরাফাত to the হজ্জ — without it, no other rite can substitute or compensate.