Katie Couric must have a lot on her mind. A source says the soon-to-be nightly news anchor has repeatedly left her purse behind in the cars of brokers who’ve been chauffeuring her around the Hamptons in search of a getaway befitting someone who’s just signed a reported $13 million– a–year deal with CBS. Couric, who’s said to be looking to spend $5 million to $7 million, has never owned out there before. Curiously enough, the famously private Couric seemed to be in no hurry to reclaim her fur-paneled purse the last time it was left behind: It took a day for an assistant to arrive and pick it up from one brokerage firm’s office. (The source swears no one peeked inside.) But Couric’s spokesman, Matthew Hiltzik, said that the whole thing “must be a case of mistaken identity. Thankfully this didn’t happen to her.” Next: What Ever Happened to Colin Quinn?