Is someone else using my Adsense client id?

Sorry if this is mentioned in old threads, but I can't seem to figure out the right keywords to find them.

I have an old channel that I've been getting tiny amount of impressions. I made sure that none of my sites are using that channel. Is there a way to find out if someone else is indeed using my client id?

Thanks!

 

Maybe it's a cached copy receiving the impressions?

 

Quite unlikely, as I've checked through G, Y and M cache and all seem up to date. Furthermore, I stopped using that channel for as long as a month or two.