Detecting vending of items from inventory tracks of item dispensing systems

An item storage system comprising:

• one or more inventory drawers, at least a given one of the one or more inventory drawers comprising one or more inventory tracks configured to hold one or more items;
• at least a given one of the one or more inventory tracks comprising:
• a sensor assembly affixed above a front of the given inventory track, the sensor assembly comprising at least one emitter and at least one sensor, the at least one sensor being configured to output one or more sensor signals proportional to a magnitude of light reflected from at least one of the one or more items in the given inventory track, a level of the one or more sensor signals changing in response to motion of said at least one of the one or more items in the given inventory track;
• and
• a controller configured to drive the at least one emitter and to receive the one or more sensor signals from the at least one sensor, wherein the controller:
• drives the at least one emitter when loading the one or more items into the given inventory track to a color associated with a type of the one or more items loaded into the given inventory track;
• determines an inventory measurement by detecting whether an item is in each of one or more positions of the given inventory track as the given inventory drawer is slid along a set of drawer tracks;
• and
• drives the at least one emitter to display an error pattern in response to determining that the inventory measurement is an invalid inventory measurement.