I would try and compromise. You have a legal leg to stand on. Like a roommate moving out, leaving shit there, and coming back a year later expecting you to pay for anything he left there. you showed due diligence. However you are not a Dick and have a moral conscience. Hence your willingness to pay him.
I would offer to split the difference, with storage charges being half. Pay the other half? Just my 2 cents.
If bj had someone leave a bike at handybikes for a year, I wonder how he would handle it?