I bought a 2006 Mitsubishi Lancer ES and only got a single key with it which doesn't unlock my car, went on ebay and bought a oem key fob for it and programmed it but it stopped working today (already tried changing the battery on fob). was the 06 ES supposed to come with 2 keys or does mine just not unlock my car?

 

Hey, I have an 06 lancer and mine only came with one key as well...
tho mine does unlock my car doors; idk if this will be any help but they are able to make copies of your key at your local locksmith...
don't quite know if this may help you but i was thinking that your key either may be imperfect (messed up in some way, chipped or made not perfect) or they have changed the starter in the car and the new key would be different from the original key.
all in all a couple different things that you can do try, get a copy of the key that you have and see if that works or replace the locks on the car itself or maybe try and reprogram the key fob once more...