Where is a Gem/Relic located after it is played?

Name
Where is a Gem/Relic located after it is played?
Details
When a gem or relic is played from your hand, it is in play until it is discarded at the end of the turn. It is neither in your hand, nor in your discard pile.
Cards
Mages
Nemeses
Other
General Mechanics
References
https://boardgamegeek.com/article/25113698#25113698