A hidden controller is not flagged by the PICO (its position just stays put). When it is seen again it jumps: the sender FAULTs on jumps faster than 3 m/s, and on a desired TCP more than 15 cm ahead ...
The parts are the same as the Micro Journal Rev.2.1. The only difference is the keyboard PCB: the Rev.2.1.mini uses the 48 keys PCB instead of the 68 keys PCB. Most components are readily available ...