What happened to Rin's Mana Compass? In Fate/Zero, Rin is given a Mana Compass by her father which she uses in her search for Kotone. I've only seen up to episode 10 but I know she'll appear in a later episode where she will receive the Jewel Pendant which becomes the catalyst to summon Archer in the 5th war and saves Shirou's life.

However I don't remember her Mana Compass being mentioned in Fate/Stay Night, nor can i foresee a situation in Fate/Zero where it would be destroyed. Given how it works it seems to be quite a useful tool Rin could've employed in the 5th war.

So I am wondering, is it stated what happens to the compass, since it seems Rin treasures the Jewel Pendant she was given, since it came from her father, and I would assume she would treasure the compass as well.
To the best of my knowledge, it's never mentioned again (not even later in Fate/Zero), aside from a throwaway reference on the Fake/states night webpage, which describes it (魔力針) as an item you could find in-game and which has Rin's name engraved on the back of it. 

From an out-of-universe perspective, the obvious reason why we don't know what happened to it is that it was invented by Urobuchi for Fate/Zero, which was written after Fate/stay night, and it's not so important an object that its whereabouts in Fate/stay night would need to be explained. 

From an in-universe perspective, I think the best explanation is that by the time of the Fifth War, Rin no longer needed the device - skilled mages can already sense magic to some extent. During the Fourth War, though, when she was just 5 or 6, she probably wasn't experienced enough to be able to detect mana all that effectively, and so the compass was somewhat useful to her back then.

By the way, 


   Rin doesn't get the pendant during Fate/Zero. It's only at the beginning of F/SN (the day before she summons Archer) that she finds it with her father's effects. Rin does happen to show up at the end of Fate/Zero (for Tokiomi's funeral); that's when she receives the Azoth sword from Kirei.