Personally I think it means that you feel that you have forgotten to do something or are worried about losing something, like your keys. No one can tell you what one object or another means in a dream. Everything means something different to different people. In our culture, your keys, the ones you were dreaming about represent the ability to get in and out of your house, or drive a car, to get to work or school or security ie, locking the door so no one can get it. I don't think it has anything to do with unlocking some mystical thing or the key to your heart or anything like that or else you would have been dreaming of some mystical mysterious key that was out of reach or something.