Sony recently pushed back The Last of Us Part 2 from its May 29 release date, delaying it indefinitely.
Due to logistic issues pertaining to retail supply of the game, The Last of Us Part 2 currently has no release date, though Sony seem to be considering an early digital release even now.
That said, you shouldn’t expect them to release a demo of the game to make up for its delay.
Given that Sony (and other publishers) usually only go live with listings of their games on the PlayStation Store when their games have confirmed launch dates in the coming months, thus making them available for pre-order, it doesn’t come as much of a shock that The Last of Us Part 2, following its delay, can no longer be found on the store.