OP, perhaps confidence was the killer, perhaps not, I wasn't there. I have misread entrance rule to VS lounges as well(arrive JFK, not from LHR but flying SkyTeam business from PRG) but when they nicely explained this to me, I said I understood but it was like going from Gucci to Kmart (SkyClub), they made a one time "exemption" for me and allowed access. A little sugar can go a long way!