If a person's foot slips upward inside the sock such that the heel and most of the foot are now in the ankle leg-shaft of the sock, what is the ruling?

Wiping over Leather Socks: Invalidators and Status Changes

• His wipe remains completely valid.
• His Wudu and wipe are invalidated, requiring him to remove socks and wash feet.
• He must perform Tayammum.
• Wiping is valid only for Nafl prayers.