Go to System Settings and change the date to when you last played. Start up the game and you should be fine.
If you don't remeber the date, change the System settings and change it to an estimated date of when you last played. Start up the game, but with a new save file. Walk around the town. If any of your dreamies are gone or in boxes, quit the game without saving, use Sysyem Settings to travel back to a farther date. Repeat until you arrive and all your dreamies are there. Then you can quit without saving and boot up an existing save file.