What are they talking about?

W: Where do you think you lost the wallet?
M: I don’t have any idea I had an appointment with Dr. Baker at nine o’clock.
W: What time did you leave his office?
M: At about 9:30 or 9:35. Then I went to the department store. After that I got into a taxi.
W: Isn’t it possible that it could have slipped out of your pocket in the taxi?
M: I just don’t know. Anyway, I could never find that same taxi again.