[altterrain]

Sounds like the cars became uncoupled and the Annie made the loop and got jammed up and over heated the motor or wireing. Hopefully, its a simple fix like replacing burnt wiring or a new motor.
I did something similar once with finding the loco laying on its side still chugging but the tender was still on the track. Lead to a bit of a meltdown of the power pick ups in the tender -

-Brian

 

[altterrain]

Battery locos are normally fused to prevent overloads to the motor driver. Power packs are usually fused and trip when there's a short.

-Brian