> Do they have cameras that can see the heat from sub-mA connections?
If it was hooked to a circuit breaker, it wasn't a sub milliamp connection. A thermal camera might have been able to see the heat from arcing at the connection point. It could have caused a hot spot visible on thermal imaging.
According to the report, on page 7[1], it was connected to a WAGO terminal block 280-681 connector. Looking that up on Digikey[2,3] finds that it's a connector suitable for 28 through 12 AWG, up to 800 volts and 24 amps.(UL 20 Amps)
According to "3 - ENGINEERING - DALI - ENGINEERING FACTUAL REPORT"[5], page 20, the circuit was DC, 110 volts, going to a circuit breaker's "under voltage release" terminal. It was 17 AWG, according to page 23.
It apparently goes to a solenoid, and if [6] is in any way typical, it's only 2-6 watts of power in normal operation. This yields a current of 20-50 milliAmps.
Here's a nice animation of the connection failure on that wire.[4]
If it was hooked to a circuit breaker, it wasn't a sub milliamp connection. A thermal camera might have been able to see the heat from arcing at the connection point. It could have caused a hot spot visible on thermal imaging.