The German secret service presented as one of the possible theories that separatists had stolen a BUK from the Ukraine armed forces. The fact that is has been stolen has not been proved. It is more likely Russia provided a BUK.
There is a lot of evidence the separatists much have known about the BUK. See this post for more information.
The BUK was seen parked on a trailer near Donetsk. A photo was made by Paris Match. That same trailer was seen transporting other army vehicles a couple of times later in separatists controlled area’s.
So there is a 100% link between BUK and separatists being aware of its existance. See this post. And here a photo of the white truck and probably same trailer as the BUK was transported on.
One of the evidences is that a BUK has been seen parked or driving in front of the head quarters of the separatists in the village of Snizhne.
The Ukraine@war blog has a very detailled blogpost about the route a BUK took at July 17. This photo was made in Snizhne.
The location where this photo was taken is geolocated as here
On a map this is located here.
Google Maps does not show the streetname. Luckily Yandex Maps does show the name of the street. The particular building seen on the photo above is numbered 13 on the Yandex map.
Now look at the name of the street. Karapetiana Street or in Ukraine Карапетяна улица
Dutch TV program Nieuwsuur went to East Ukraine in October. The program tried to find eyewitnesses who saw a BUK or fighterjet. They went to Snizhne to get allowance from the separatists for filming. They had to visit the separatists headquarters in Snizhne.
The reporter said the HQ was in the same street as where the BUK was seen.
As you can see, it is in the same street as the photo above.
So it can be just a coincidence the BUK drove in the same street as where the separatists HQ is located. However this street is not a thoroughfare.by