Why do people believe Vaas from Far Cry 3 is alive if...?

[The Walking Dead]

Jeffrey Yohalem was asked on Twitter, whether or not Vaas is dead, he responded with:

"Sam and the privateers confirm Vaas's fate. What reason do you have to question them?"

[Jon]

Yep one guy said it so its obviously true i mean its not like he was killed in a dream and his eyes opened after he died.

[CZack]

You never get to see his body after his death.
Jason was in a fucked up state when he killed him.
Vaas eyes open and stares at Jason after he collapses.

Sam and the pioneers confirm Vaas death.
Citra confirms Vaas death. In other words people say that he is dead.

Second of all. After Jason collapses, how does he end up at Citra's place? If Jason killed Vaas in his base, wouldn't the pirates take him? Or did he kill each and every single one of them? If so, why did Citra and her Rak'yat wait for Jason to take out that base all by himself, AND then charge in, just to get Jason? Or did the Rak'yat have spies inside Vaas camp? If so, Jason should have known and since he did, he must have killed them. IF there were any.

My point is, it is not certain that he is dead. Just because people "confirm" it, doesn't it mean that it is true. There could've been other things outside the box, like Vaas faking his own death. Since Vaas is mentally ill and broken by the torment caused by Citra and Hoyt, he must have wanted to run away when he started to see what Jason Brody was doing.

Since Jason and Vaas are very much alike, both monsters and both of them had to go through the same thing, for example at the end of the game. The difference is that Vaas teamed up with Hoyt.

When Vaas saw that Jason took a different path than what he did, he realized that there was a third option, something better. So he started to become all this freaked out. More or like, more crazy.

Now there are other theories and shit like that, but this is from my belief. Plus, a great character like Vaas should not die just like that in a fucking hallucination.