SteveO, you could do a little backward search to see where that song turns up. I keep a half-dozen browser programs in my computers but they're not all logged on to every account. Sometimes you see useful stuff when you visit a place as a visitor, not a member. I suggest you use a browser that you don't have logged on to your SoundCloud and do a search both on your song name at the site, and also do a general Google search on your song title or even fragments of the title. If you can't get into SoundCloud without being logged on that's fine, but poke around in the search results to see if other sites are linking to your song.

I have only visited SoundCloud a few times, but they must have a dashboard that will let you look more closely at some of the places your song has been played. As Haruo pointed out, links to your song will show up as hits, so a facebook page liking your song can keep it in play for a while. If someone has linked to it for background music for another site you will also discover that. This is borrowing your bandwidth to augment their site. (At least this does link back to you, versus their simply lifting it and embedding it in their own site without credit.)

Good luck sorting it out.

SRS