Okay I can't get rid of this D-02 Receiver from Tyrant castle quest line.

I can't toss it. And it doesn't work. At least I don't think it does. I've tried all the maps in the castle and nothing works.

Edit: This one is a receiver and it just sits there.

So, you've used it at the map before the enter roof boss, and at the map before you enter the lab basement boss? After checking my quest now, I see a transmitter 03 that I'm able to get again, not a 02 model. Before the castle quests, I remember entering the forest area the last map on the left side, that's where I used the receiver.

edit: 2nd to the last forest map