For it to die from starvation is not possible. imo, starvation is a obvious sign where you see their bones, and notice a paper thin stomach, pretty obvious to spot.
a lot of fish are caught with cyanide, I think to slow them down to catch them easier, a lot of times they are fine for the few weeks in transit and a few weeks in the stores tank, then they slowly die a few week's later in the person's tank that recently bought it.
one way to protect yourself, from this, is to maybe custom order and reserve a fish, while giving a deposit. make sure you go to the store when it arrives, then request that it is in their tank for around 3 weeks minimum, before taken it home.
Request to see it eat, make sure it is swimming actively and is alert to the persons hand that is about to grab it for you.
also do all your research and ask a lot of questions and look at a lot of healthy looking exact pics from the net of the fish you are about to buy, to get an idea of it's natural brilliant color.
Ask about that fishes minimum tank size, it's comparability with your existing fish, along with it's diet.