The antennas are just not that good, and one has to be careful where the key is placed. I will just have to turn off auto-lock.
I always have the FOB in my pocket so that it can never be in the car without me. I love the convenience of auto-lock. My wife, however, always puts the FOB in a different place all of the time - sometimes her front pocket, sometimes her purse - so it makes it easier for her to forget where it is.