I think that you may find this occurrence with various electronic devices. I can't say for sure one way or the other if my LG Voyager has ever had this happen, or my iPod Touch 32GB 2G, or my LG Ally that I had for about a week, etc. I can say that the thought of this having happened crossed my mind a few times every now and again. I may have thought I noticed something odd about my recent battery charge for something, but I don't think anything ever seemed concrete enough and I just dismissed it as one of those, "ghost in the shell," type of situations.
I will post here commenting on what I experience once I receive my own Droid X, however.