Definition: Physical touch, meaning the touching of a physical object. Not objectively human in nature, just anything touching / covering the sensor or switch.
The above line is included as every search result I could find, had to do with capacitive touch sensors and human-touch.
Instead, this is much simpler. The sensor would be placed at the bottom of the object, and we just need to detect if the object is set down against something. This could be a table, or anything really. I've researched many types of sensors, but most are far more sophisticated than what is actually required here. (Most measure distance, while we just want to know if the sensor is covered or not.) Due to this a switch may be preferred, however the durability of the switch is a concern especially if it's meant to stick out of the bottom of the object.