I went and tested this with my star rocket ID #KMR5A6JY

Here is a video of it happening

 

magic elytra does not need a star rocket to operate it, you just use your hand and left or right click it (dont remember which one). anyways idk why it would remove your star rocket but just letting ya know.

 

@YandereDevil take notes
I just filmed the video because he had no proof

 

We have fixed the bug with Magic Elytras consuming Star Rockets.
If you lost a star rocket due to this please contact @ClarinetPhoenix and she will regenerate one for you.

In the meantime, it seems Magic Elytras themselves are broken for whatever reason.
We are aware of this and added it to our development todo list.

 

Magic Elytras have been fixed and will be functional again after our next maintenance.