Check the hobo area!
Here's the main steps:
-talk to Fawn in the condo, get the Cassie rescue notes
-go round talking to NPC's that you have good relationships with, and get their help.
-Specifically talk to Arlene, then go to the hobo area in the slums
-get the hobos' help (make sure they actually deliver, and you'll need to sleep to move the clock forward,) then return to Arlene
-after that you can rescue Cassie!