A monitor and method for reasonable confirmation of a vend from a vending machine includes a set of optical emitters positionable on one side of a dispensing area and a set of optical detectors, adapted to sense the optical energy of the emitters, positioned on an opposite side of the dispensing area. The emitters are spaced apart from each other and mounted on a supporting structure that can be installed on the one side of the dispensing area in a vending machine. The detectors similarly are spaced from one another on a supporting structure that can be installed on an opposite side of the dispensing area. A controller operates the emitters to individually turn on and off in a predetermined sequence. The controller checks for falsing of any detector during the off periods and monitors if any detector is blocked during the on periods. Upon sensed falsing or blockage, the controller generates an output signal. The output signal can be communicated to the vending machine to stop any further attempts to vend a product.