The day after the update Wisp can be found. If Katie is in your town Wisp will not appear.
I spent 30 minutes running around town looking for Wisp for my 4th player. It clicked that Katie was in town. Sent her out and Wisp appeared right away. If you have more than one player Wisp will give the lamp to one player. You have to wait the next day for another player to get the lamp.
You can use the lamp in other players house in your town. While trying to read the card Wisp went back into the lamp. A villager was at the door. Stopped using the mayor house and drop by one of my extra players houses to read the card.