This generosity of NewEgg has been confirmed by Reddit user "littlestminish" and by others in a thread titled as "PSA: For everyone who received Batman: Arkham Knight with a Nvidia GPU on Newegg, they are giving away MGSV: PP free of charge."

According to littlestminish,

"All you have to is call Newegg up and give them your Batman: AK order number and they'll send you a copy of Metal Gear Solid V: Phantom Pain. Note that isn't a one per customer situation, so if you bought SLI and got 2 copies of the game, you will get 2 copies of Phantom Pain."

Not only this, NewEgg is also offering GeForce Assassin's Creed Unity bundle buyers a free copy of Metal Gear Solid V: The Phantom Pain.

"I have seen proof that AC: Unity is also a game they will give you MGSV as a replacement for. Have fun on the line with support folks"

If you made the purchase from BestBuy and not from NewEgg then follow the steps provided below and they will offer you a 60 dollar Best Buy gift card:

Call Best Buy, don't email or use whatever chat they have
Get transferred to the promotional department
Mention the poor state of Batman, that is has been pulled from Steam, and that sites like Newegg are offering a replacement copy of MGSV
They say that they can't give away the game, but they'll give 60 dollars in a gift card.
Now that we know this works, make sure you say you have reports of other customers getting this deal

http://www.gamepur.com/news/20053-retailers-giving-free-copy-mgs-v-phantom-pain-buyers-batman-arkham-knight.html