In Act One, why does Beatrice ask about Benedick? What is the real 'reason'?

Beatrice and Benedick have a past, you see.  When they do come together again after the battle, they engage in a battle of wits.  At the end of which, Beatrice mutters "I know you of old."  Futhermore, in the party scene, Beatrice will admit that she "lent her heart" to Benedick a while back.  Both this things imply a romantic history between the two characters.