I assume the elevator uses a sort of keypass? Go in soaking wet wearing nothing but your swimsuit and holding your phone. You can put on a swim cap and goggles for your disguise. Pretend to be really annoyed. Tell the concierge that you had been swimming when you got a call from your daughter/sister/wife (any woman close to you) that she'd thought she was going into labour but it was a false alarm. Say something borderline mysoginst and passive aggressive as this will help in creating the illusion that you're a dolt. It will be obvious that your keys are in the pool locker room and he'll have to let you up.