confused ? you bet ! 'transliteration ? " yeah, had to stop and look that one up.
I would start with the premise that any physical contact devices can be damaged.
also physical devices can fail from use or poor manufacturing.
also, like the beam/break, any single point detector misses 99.99% of the rest of the space.
look at your refrigerator door. or car door. it has a switch that senses when the door is open or closed.
simple button. very easy to put 100 or so into one Arduino with some supporting chips.
car park is often a metalic object detector. the presence of the metal object being a car.
this too could work
a simple ceiling mounted IR beam/break could work. item placed might break the beam or reflect it. could be problematic
also a ceiling mounted ultrasonic distance detector.
some from of load cell could be used to monitor the weight of the shelf. as long at the items have enough weight, it might work. more expensive and more electronics and more elaborate, but more informative.
a 'barn door' The floor could be hinged in the front and be sprung in the back. weight on the shelf has it sitting on the stops, but pressed the switch when it has weight. not a load cell, but anything that weighs enough would activate the switch.
you did not say if this was a school project and if there are other requirements.