Unfortunately you probably don't have a valid claim.
It's also up to the owners to ensure that their property is correctly secured, particularly when they have guests staying. Trusting guests to always do the right thing and lock every window, door, etc is not realistic - as much as we might want it to be.
A garage, where guests are storing bikes and where other expensive items are kept...there would be an expectation that the home owner would check to ensure it was locked correctly when leaving the property, etc.