This is a story told by Lexi to Cameron to lie to him about where to get her instructions about creating a wild goosechase. Cameron listens because he is desperate to Olive to leave him alone in the episode The PhANTom Locker.
Lexi : Now head downstairs to the sub-basement. Go in the boiler room and look behind the water heater. There you'll find the key to a box and inside that box will be a map of San Francisco. Now, if you hold that map up to the sun at exactly dawn, it will reveal a trail to a mini-mart across town. Ask for a mango slushie. The clerk will guide you from there.