Brand new battery drained

[RubySlippers33]

I have a 2 month old 12 plate Toyota Yaris T-Spirit with smart entry/start. I went on holiday for 2 weeks, leaving it in my garage and when I returned at the weekend, the car wouldn't start at all. It wasn't especially cold or anything like that while we were away. I 'phoned the dealership and described the "symptoms" and was told that it sounded like the battery had drained and I should call the AA. This I duly did and sure enough, the man from the AA confirmed that the battery was dead and got the car running again.

I've booked the car in for next week and intend to make an issue about this - I suspect, without having checked yet, that batteries won't be covered by the warranty. But surely it isn't right for a 2 month old battery to drain completely after 2 weeks? Has anyone else experienced this? Does it sound like something that "just happens"? Should I be insisting on a new battery at their cost?

Thanks for your help.