The envelope Jim pulls from the bottom of the phone is very small so it fits in the small space in the phone, but the picture he is holding of Groat is full-sized and has no fold marks, so it couldn't have fit in that envelope.
Trivia: Jim picks up his briefing on a tape recorder placed within a phone in a phone booth. the tape plays over the phone.
Jim: Then we're all set... except for the typhoid. Who has it?
The phone booth scene at the beginning where Jim gets his information is an almost exact re-use of footage from earlier in the seasons episode "Trek", with obvious changes made to the information given to Jim to make it pertinent to this episode.