Toddler dropping the F bomb

Yes, this really happened.  My lovely little Lilah (that beautiful little girl) looked me in the face and said that word.  She said it several times, actually, because I couldn't understand her at first.  She had some ink on her hand, and she was holding it out to me asking "whadafrogusat?"  I didn't understand her, of course, and she kept saying it over and over, a little clearer each time until she slowly and distinctly said, looking into my eyes, "What the f#@& is that!" Hmm. Not good.  I told her, that wasn't a good word to say and that what she meant to say is "What is that?"  She repeated her question without the expletive, I explained that it was just ink, cleaned it off, and that was it. That still leaves me with the question of what to do.  I’m not going to say I don’t know where she heard it.  Her daddy has quite the potty mouth, and I’ve been known to let go of my tongue from time to time.  We’re working on it. My husband has been trying pretty hard, but, apparently, she still hears words she shouldn't  occasionally.  We tried the swear jar, but who has cash or coins on hand these days?  It's not nearly as effective when you're keeping track of the toll in your head.  I guess all we can do is keep working on ourselves.  
Have any of you had a problem with children picking up on swearing?  Do you have suggestions for helping parents remember not to swear?  Was my response to her enough?  We haven't had a repeat offense yet, but I don't know.