my passive-aggressive line: "i'm sorry. i saw there's a parking lot with several dozen/hundred places for parking a car, but i was unable to find a single place for parking a bike. if you can show me where the bike-parking is, i'd be happy to use it."

if they give me the "not my problem" routine, then i just note their name and let them know that i'll be advising their supervisor that they're chasing away would-be customers on bikes... have a nice day