You don't need to do anything. This is a gift from your father to you. Under US tax law, gifts are not taxable to the recipient. (If the giver pays tax in his home country, that is his problem.)
Gifts from non-US persons only need to be reported by the recipient if the amount is more than $100,000 in a year (or more than $14,000 if the gift is from a foreign corporation). So you don't have any responsibilities regarding this gift.
Now, for IRS purposes, this will look on paper as though it is a gift from a US person (the buyer) to you. In that case, the giver is required to file a gift tax return if the amount of the gift is more than $15,000 per person per year, but the recipient still has no reporting or tax responsibilities. The fact that it looks like a gift from the buyer to you, but was actually a purchase price paid to your father, is something for the buyer to deal with, not you.
(Also note that if the reason your father did it this way is to avoid paying his own income tax on the proceeds, that is between him and the tax authorities of his home country, and also does not involve you. However, I would save all the documents and emails related to this purchase and gift for 7 years, just in case you need to prove something to the IRS.)
