What subtle hint is used to reveal that Gat is dead in the novel, We Were Liars?

Cadence mentions when she first sees Gat and the other Liars, Gat is wearing the same t-shirt that he wore two summers again. It is unusual that a teenaged boy would be able to wear the same shirt he’d worn two years prior. This is one of the first hints that Gat is really no longer alive.