Uh Oh...that's not supposed to happen!!!

It's Monday, June 20th, 2011 and I'd just gotten home after teaching summer school and running errands.  When I tried to unlock my back door to go inside the entire lock mechanism came out WITH my key!!!  Now, I'm no expert but I am pretty sure that THIS is not supposed to happen!!!  When I mentioned this to other people everyone quickly jumped to the conclusion that someone had tampered with the lock trying to break into my house.  I wasn't so convinced because the lock had been giving me trouble for weeks now.  Every time (before this) I

 had to jiggle the key around to get it to turn and the last couple days I actually had to steady the knob with my other hand to remove the key.  It seemed to be getting looser and looser until today, when it simply gave up and fell out I guess?!?  I gotta get it fixed one of these days though because I've already locked myself out a few times by twisting the bottom lock as I leave the house (out of habit) but from the outside there's no way to untwist the lock so I then have to go around to the front door to get in!  Problem is, installing a new lock means a new key or a locksmith to come out and key it the same as the rest of the house and all of that is just a pain--hence I have not yet fixed it!