Friend signed in to my iPad with premium using facebook, now I can't sign in with facebook

[jonbaca]

I brought my iPad to an event, and because I only have the a free Spotify account, we wanted to stream music without the commercials.  I signed out and a friend of mine signed back in using his facebook credentials.  Now, I can't log back in using my facebook credentials.  

I tried searching other posts here, but all I find is desktop solutions or *gasp* what seems to be no solution for disconnecting my friend's premium account from facebook login.

Please help.