I had someone ask us for a "silent" ringtone!
At first, I didn't get it, but it makes sense. You can assign it to a number of people (your "ex", your boss, someone who always calls at the wrong time, or if you work in a sensitive environment, you don't have to remember to set the mute switch, which also mutes many apps, which may not be desirable).
So, we added it!
Are you sure they weren't talking about this?
My iPhone tends to "lose" the ringtone assignments and turn them back to the default ring.
I got tired of re-setting all 30 of them every few weeks, so I don't use custom ringtones anymore.
Too bad, I really liked them.
OP, correct me if I'm wrong, but it seems like you're asking what do you have as your current ringtone, and why do you have that song/sound?