With the new cars thats what happens, I was using the raido in my 09 traverse while cleaning it and the battery went dead. Key would not come out. As for leaving in the garage for a month and the battery going dead. I have to agree with Envy something is drawing power. one way to find out is hook up an AMP Meter and see if you have a current draw. You would have disconnect the negitave cable and hook up the AMP meeter between the cable and battery post. If you see the meter to to the discharge side you have a power drain. You will have to get it running first. I have had my Camaro since Jan 11 and have left it in the garage a couple of time for 30 days or more with out starting and the battery did not go bad. You could have a bad battery. I would take it to the dealer and have them check it out.
2013 LT2/RS, Crystal Red Metallic, TAZ Jr.
2016 H-D Ultra Classic, Black Fire Purple, (PPE)
2015 H-D Street Glide, Superior Blue. (Old Blue) Traded
2012 Big Horn, RAM, Crew Cab, SLT, Dark Cherry Red Pearl (Betty Boop)
1998 Honda Accord 2d, daily driver.