It does seem as though Vibe passes are no longer widely available for purchase on embarkation day for most cruises. Although this may not be an official policy, on all of our recent cruises with NCL, Haven guests were able to obtain a few Vibe passes after speaking with the concierge, even though Vibe was sold out. Of course, I don't know if these passes were actually "held back" or if additional passes could be made available in certain circumstances. In my experience, this also applies to restaurant reservations, spa passes, and other comparable services. Based on this, one might surmise that if someone had a well-placed contact among the ship's staff, they may be able to make it happen as well.