Strelkov’s update says he doesn’t know who the tank claimed belongs to. It may be the T-64BV his units destroyed a couple of days ago.
That said, the Horlivka group (Besler) also captured a couple of T-64’s last month, so it could be one of those. The three T-64’s from Crimea are all reported to be around Donetsk, but that could also be Besler.
Maybe it’s one of the tanks that RT reported swam up the river to get there?