In the beginning, the Sea Duck is at Hire for Higher, but then Baloo and Kit are flying the Sea Duck back to Cape Suzette.
Rebecca should know better not to rely on Baloo to deliver mail that would win her $100,000 in a contest due Baloo being usually incompetent. She should've also told him that it's important for the mail to be delivered by tomorrow, despite her trust towards Baloo being strained.