For the timeline:
>15 July 1975
Luna reacts to the Apollo–Soyuz Test Project. It is speculated that she reacts because it marks an end of the Space Race.
http://s16.postimg.org/61rfxz445/tumblr_nofl5c_Y3yt1tf6bclo1_500.png
http://s14.postimg.org/47pkpj27l/rocketmare.png

>? ? 2015
Luna visits Earth, and is briefly caught on a security cam. Presumably she recovered the Gameboy.
http://penumbrabard.ponyblogs.info/post/111420088478