I've had Boone as a companion since I was level 7 or so. Recently I aquired Rex and started doing some site seeing and while exploring a cave, Boone just vanished. Although, it still shows his perk active in my perk list. I read in the sticky topic that you could wait seven (in game) days for a companion to return to their original spot. Does this work for a "bug" like the problem I'm having? Anyone else have this problem?

you can try either of following sulotions:
1. sleep for 7 days in game
2. go the vault 22 and take the elevator(need repair skill 50)

hope your problem can be resolved, otherwise you will have the same problem as my ED-E disappearing.