Screw Loose Roundhouse 2-6-0

[Sunshine Express]

Drivers Check Your Engines - That is if it is a Roundhouse Mogul 2-6-0.
I was looking at a part of my layout trackwork this morning thinking what maintenance should be done,when I spotted a tiny black screw with washer lying between the sleepers/ties.
On inspection it was bright black shining,looked brand new.
My first response was to lift off my new MDC Mogul standing on an adjacent track,and there was the answer-  the screw came from the rear bogie/truck.
Happily no harm done since the screw must have come off from last night,s running,without the truck coming adrift.
I checked the tension of all screws underneath,and only one on the other tender truck needed a slight tighten.
Hope this "screw loose" post is helpful .