I am not sure PayPal or eBay really have any responsibility to be honest. You simply used their services to buy something. They haven’t withheld any details from the police or obstructed anything. If you had posted a cheque would the post office be liable for shifting your money? It’s bloody bad luck that it took so long for the police to arrive (not saying they must have say on it by the way) but I have a horrible suspicion that regardless of whatever anyone thinks eBay or PayPal should do, they will have an awful lot of experience of this kind of thing and their processes as probably set up to ensure their liability is very, very limited.
Doesn’t help you get your cash though, is there an equivalent to the motor insurance protection against uninsured drivers for other stuff? Never heard of one, but I have never had to look thankfully. Probably worth a trawl through your house insurance, and give them a call as they stick all sorts of extras on to be more appealing that you might not have noticed.
Hope you get some restitution…