We first moved into our starter home in 1996. A year later, I went to our detached garage early one morning to get my Cannondale to ride to work, and discovered the big garage door wide open. My C-dale was still there, but my and my wife's Trek (2120/1220) had been taken. We were first time homeowners and didn't have a clue as to how the thieves gained access. The police explained the most likely scenario.

Turns out the previous homeowner had left the garage door opener on its default codes. Thief had probably driven through the neighborhood with a default remote and clicked like crazy to see what opened. We learned that one the hard way.

This may sound extreme, but I always recommend storing bikes in the house rather than detached garage. Makes the thief take the chance that someone will be home, and that changes the stakes from burglary to robbery. It's much easier to break into a detached garage than you might think, and the chances of coming across the homeowner at odd hours are slim at best. I am truly sorry for your loss.