they only get paid to sell you a truck, so they will try to get one for you. but it is totally up to you to accept what they are able to get (if it's different from the original.
I will say that it makes it tough for them to get the truck in a situation like that. not only are there few of them out there, but when they call, they need to basically say, "you have a truck I have sold, can I get the invoice sent to me?"... if they just call and ask, "you are showing a truck, is it available? should be? ok, i'll get back to you if my customer wants it". then, by the time they call back, the manager has talked with the sales floor and they say they can use it or are showing it, so now it becomes unavailable.
and rocket, kidding aside, dealers *are* there to make money, not screw people over... might seem like the same thing, but they are a bit different! but yeah, there are some dealers who more than blur the line, i'll give you that!