if you are currently occupying a planet, then you are limited by the abandon timer...
but... you can use starchart purgers on unoccupied and enemy planets... you do not have to take them first...
if you purchased an artifact (and know you purchased it) and can't find it, contact Dan directly.. here's instructions on that
http://galaxylegion.com/forum/viewtopic.php?f=5&t=583