Well, the courier is to blame if they saw fit to leave the package with a neighbour (unless your buyer left instruction for them to do so) and in your shoes I'd be claiming from them.
I've experienced the same issue as a buyer a couple of times with couriers leaving packages with workmen working at a nearby holiday home or the holidays makers there. I never got my packages back because the workmen had by then disappeared and the holiday makers gone home (with my item, presumably), one item was a new xBox. I ended up issuing not received chargebacks in order to get my money back.
