Simple Question

Okay, I was doing the Dustia trick (where you use Phoenix Downs on Dustia to gain a crapload of MP). Anyways, at one point I kind of stayed too long for the kill to see it, and then when I went back to the previous area and proceeded back to the Corriders of Sand, he was gone. My guess is that I stayed too long and he died and wouldn't return.

My question is simple. Can Dustia return? Or is he gone forever?

Yes, you can kill Dustia again. You'll need to leave the Westersand though. Return to Rabanastre (you might want to save and restart while you're there, just for good measure, I'm not sure it it's required), and then when you return to the Westersand, you should be able to make Dustia appear again.

There are some Rare Game that will disappear forever after you kill them, but Dustia is NOT one of them.

The ones that DO Vanish when they are killed are called "trophy Rare Game". Don't trouble yourself with them until Much later in the game After (SPOILER)Draklor Laboratories

I have a simple question too. What are some easy ways to make rare game monsters appear? Is it possible to start a game where some never appear?

It really does depend on the rare game, Dustia for example only appears when you have 10% health remaining, while others have you killing 20 wolfs for it to appear ( Lindbur Wolf)

So research on GameFaq to find out criteria about it.

I'm pretty sure he's gone forever.

my favourite is in osmone plains where you haveto kill all the Xu to get that massive smurfer..........Wait.... thats a hunt... ignore me