It would be helpful to know why you were even keeping it in the building in the first place, if you had locked it up, etc.
Most places aren't going to accept liability for monitoring your $1500 bike when you come to work -- if you bring it, it's your issue, and it's your responsibility to lock it, etc. Unless there's something in your employment contract or their policies that says something like there's a secured employee area and they're responsible for maintaining it, etc., and they expressly gave you permission to keep your bike there... I wouldn't hold my breath.
It's possible they have some kind of insurance to cover it, but I expect they're going to say it was your responsibility unless you can show they were somehow super duper negligent. At best, you might be able to convince them to give you a good deal on buying another bike through them. Highly unlikely they're going to be obligated to pay for you bringing that into the building and locking it how you locked it (or not), etc.