User blog comment:Chaosian/Primary source for Tower Pack DLC/@comment-76.175.195.131-20130912020459/@comment-1932315-20130912194100

The idea is that D6 is "found" by Artyom (who is 20) and all them in 2033 after it is lost. It being lost, after Metro Command died off in, say, 2020 (when the Tower Pack takes place). Artyom is in no way affiliated with Metro Command, so his age is of little relevance.

Think of it this way: the real D6 is not lost right now, the Russian goverment has control of it. After a war the people in it stay around for 7 years, and then all die off. It sits emprty for a while until some guy and his friends come by and find D6 again. That's essentially the sequence of events.