"Typically, whenever the Russkies send something over the border, they claim they captured it first,"
There is no evidence that this is true, however, except from Russian media.
Now where is your source? Nato?
Yes, it is NATO, as well as photographs seen of the Buk traveling through Ukraine and then later fleeing back to Russia, thus implying that is where it came from.
The pitfalls of FINT (facebook intelligence). The photograph of Buk was taken in Krasnoarmeysk, town under Kiev control.
FINT forgot to edit the photograph and it shows the billboard ad for the Krasnoarmeysk car dealership, along with the dealership address.
Perhaps it is the time for the T shirt reading something like this - "My tax dollars fund NSA and all I got is this crappy photograph from Facebook"