Deleting files from FCP X 10.2

Hi,
I am just returning to using FCP after not using it since FCP 7 or below. I'm working in FCP X 10.2.1 trial version. I love it and plan to buy it.

I'm taking the wonderful tutorial with Michael Wohl on MacPro Video which suggested I try things. Oops. I tried something that really messed me up. I think I created a double master clip which is huge! I moved the clip to the trash from the FILE menu. The media is still appearing in my project in the timeline and not appearing in the trash.

My hard drive (iMac 10.10.X Yosemite) has only 2.5 gigs left. Where did this video go and how can I clear it from my hard drive?

Thanks,
Kathy