Continuity mistake: In the bike chase scene the bikes tires change from normal road tires to knobbly off road tires.
Continuity mistake: In the scene where Ben Affleck and Uma Thurman are going back to destroy the future viewing machine, the Mexican security guard is behind Ben Affleck then suddenly is in front.
Continuity mistake: Seattle seems to have a great number of blue Dodge Neons. During the motorcycle chase scene, we see a blue Dodge neon sedan no less then 5 times.
Continuity mistake: When Michael gets on the at the transit station, the camera pans down the bus aisle. The thief is not in the scene. The camera pans back to Michael then back down the aisle. The thief is now sitting in his seat.
Continuity mistake: Throughout most of the movie Michael is wearing a white dress shirt that no matter what he does never seems to get any dirt or markings on it whatsoever. (This mistake pertains to after he does the 3 year job).
Answer: He could have got someone to obtain the key and bring it to him. The same goes for much of the other stuff in the envelope.
Xofer