how to delete media from imported media?

Hi,

I have pasted a 5 sec multicam clip from another project...I didn't know that FCPX would copy all the media from the other project into my current project!!!
It took more than half an hour to import everything and I had to stop working for the time being.
I tried to delete the media...nothing. FCPX doest let you because "it is in use".
Deleted the pasted clip from the timeline...tried to delete the media from the library...nothing! Error message: "FCPX can't delete multicam or compound clip because it is in use"(or something similar).
I have checked again and again, and the clip is not anywhere in the timeline...why does it say it is in use?
How can I delete this unwanted media frm my project???

Are you copying between Libraries on the same hard drive, or on different hard drives?

It is on the same drive.
But why can't I just delete?

Because a clip you're trying to delete is being used in some other Timeline.

BenB, you mean the clip is in another project on the same event right? It makes sense.
Or it won't be deleted if it is in any even in any library?