Never mind, I somehow complete it. What happened was:
Step 1: talk to Cecily about the rescue mission, Cecily will ask you to wait 5 days before giving her your answer.
Step 2: wait 5 days
Step 3: when Cecily is ready to hear our answer, WAIT ANOTHER DAY, Milo will contact you then.
Step 4: talk to Milo and rat Cecily out to him
Step 5: "help" Cecily with her mission.
Step 6: profit.
So, either the guide in the Wiki is out-of-date, or it is a bug. Hope this help, thank you.