In The Atrocity Archives, part of the Laundry Files series by Charles Stross, the protagonist, Bob Howard finds a Kettenkrad on the other end of a portal.
Some kind of small vehicle, like a weird cross between a tank and a motorbike, is parked against the wall, dusty with a sprinkling that isn't snow.
Some time later, it's gone.
(...) the little half-track thing with a motorcycle's front wheel is missing.
Bob gets home, there's a Kettenkrad engine on his kitchen table.Later it's confirmed that this is the engine block of a Kettenkrad, belonging to one of Bob's housemates.
The front hall is full of petite tank tracks. They're about twenty centimetres wide, covered in dried-up mud, and run past the hulking Victorian coat rack and the living room door to stop just short of the kitchen.
There's most of an engine block on the kitchen table.
Where does it come from?
Reading back, I think I just read too much into the missing and resurfacing Kettenkrad, excluding the possibility that it's just a weird coincidence. Also, I thought Morris to be one of the casualties.