If your breaker is an Eaton 20A AFCI/GFC1, (BRP120DF, for example) you can determine the cause of the trip from the number of LED flashes on the breaker. They have a video for doing that. Or see,
this There is also a lawsuit against them for two series of those breakers. I have replaced 3 this year that started tripping intermittently, including one that had nothing plugged into any of the sockets. Eaton will replace the breaker free of charge (BRP120A1CS BR PON, the older one is discontinued. 3-5 days shipping). The replacement breaker is about $68.00 at Lowes.
As to labeling the circuit number on the plate, you can label it on the inside of the plate. Looks less cheezy and you only have to take out one screw to see it.
HTH.