When you come downstairs Bud may be laying on the ground (might not happen yet but always happens before Cosmo Event). Talk to Bud and Lisa.
Enter Domina and go to the Marketplace to talk to the fortune teller.
Enter your Home and go upstairs to see that Cactus is gone. Read the note in its pot.
Enter Luon Highway and go talk to Gaeus.
Enter Jungle and go talk to Selkie (Upper Left from the Forested Ruins).
Enter Geo and go to the Magic University. Talk to the student in the entrance hall.
Enter the SS Buccaneer and go (left, down, stairs, left door, stairs) to talk to David.
Enter Domina and go to the Outskirts of Domina. Talk to the Pelican.
Enter your Home and take the Cactus out of the mailbox.
Return home, talk to Lil' Cactus, go downstairs (watch him write the Event on the leaf), and go back upstairs to save your game before continuing.