Someone tossed, or the wind blew, a plastic shopping bag into Grand Army Plaza, and the bag came to rest at the feet of this sandwich board. Since then, the wind has probably carried the bag elsewhere, to other streets or into the trees, where lots of bags like this one get stuck.
Wherever it may have gone, this bag will outlast by far whatever gathering of love and soul the sign in Grand Army Plaza advertised.
Paul reassures us in 1 Corinthians that love will endure — that it will bear the weight of the world and outlast all things, πάντα ὑπομένει; but plastic is perdurable, and takes an awfully long time to disappear. Long after those who may have gathered here are gone, this bag will remain.