new car question

I ask because my car went dead over nite, with the key either in acc or run position, and since I don't know which, since I was not the first one in it, I thought a definite answer would help to troubleshoot it. The battery was dead enough so that the key couldn't be put into the off position. It didn't run out of gas. I guess I'll just charge the battery for a few hours at a couple of amps, and then test it. If it checks out ok then I'll just chalk it up to oh well, and see if it happens again. Thanks for your replys.