ANSWER: Ice in the flush valve assembly
That black thing in the picture is not a pipe, it’s a home inspector’s flashlight resting on top of a block of solid ice in this bathroom’s toilet flush valve assembly. The rear tank on the toilet holds the water that flushes through the toilet and sends everything to the drain pipes. Needless to say, this toilet will not flush. The lesson here is pretty simple: toilets don’t operate without water.