Sometimes, it can happen. It just doesn't happen a lot. My biggest killer is when I forget to turn the plane switch off, that has happened a couple of times. If the battery was really low when you put the plane away it could have gone down. A good charger/cycler may get it back up if it isn't too bad. Without a meter you really can't tell. I have left batteries in my shop for a year or more and they came back up after a cycle or three. Just a few months shouldn't have hurt it, sounds like you had a bad one, a short, or maybe it's your charger? Could be a lot of things. Borrow a meter and see what it is showing, if it isn't totally dead then borrow a good charger and give it a try.