I googled this problem and found a few walkthroughs for it, and I also noted a number of people saying that they couldn't seem to get the keys and get back upstairs fast enough.
One person who made it through this sequence said the following:
Okay, have Frank waiting at the top of the stairs....switch to Joe to ring the doorbell...switch back to Frank, grab the keys and then click on the wall on the side of the stairs where you see the footprints...that will do it....
Apparently you need to do this in approximately 12 seconds or less.