One trick with key access elevators is that in every hotel, there are always 1 or 2 floors that are dedicated to conference rooms, a mezzanine floor, ballrooms, a spa or gym ot even a secondary lounge/restaurant, that isn't restricted to key access. Even the 5 star ones that everyone always assumes is completely inaccessible, aren't.
For instance at the Trump, all floors are restricted, however the 31st floor isn't because it houses the America restaurant.
Ask the gent to meet you on that unrestricted floor, when you figure which one it is, if you feel uncomfortable going to meet them in your hotel lobby.
Most hotels have them between floor 2-4 though, as a general rule of thumb.
Even if you are going for an outcall and you don't know which floor it's on, it's way easier to figure it out once you are in the elevator by pressing a few buttons, away from curious front desk staff in the lobby.