Wait a sec, you can book any VS flight as a reward, not just the codeshare flights?

I changed a reward reservation a few months ago to London and instead of returning from LHR on the 4pm VS departure (VS1), I was only able to select the 7pm departure (VS17). When I re-booked I asked about the flight I wanted and they told me they don't see it. I am guessing because it was not a codeshare.