I've been through this trunk/battery issue. Twice. (2008 Ltd Roadster). It happened shortly after I bought the car. Turns out that if the trunk is not tightly closed, the battery will, and does drain. The thing is that you think the trunk is fully closed. And it isn't. And the spoiler does deploy. The forum really helped scope out this issue for me and I passed it on to the service advisor.

I learned the hard way to check that trunk! I did get a new battery out of the problem. Initially the dealership thought the original battery had simply failed. The problem + solution was discovered on the 2nd go-round after the new battery 'appeared' to fail.

Alicia