are you an equity or mu member - you might be covered for some of the money by your insurance. they might sue the pub for you.

Most contracts are generally pretty crap - more holes in than a swiss cheese, but you might be covered by the contract with the pub.
was there an agent involved in the gig? if so there was probably some sort of contract - get your hands on it!

i think you're wasting your time reasoning with the kind of arsehole who would jump on a Martin - whatever the joyous mood of the evening.

like the guy said - get the police in. chances are, they haven't got a pot to piss in, so even if you were awarded damages - you might be waiting a while.

there are all sorts of probable outcomes but in the short term, your friend is going to want a guitar - and there was some sort of obligation to keep it safe, having borrowed it. I suppose it depends if your mate, knew you were the sort of guy prone to this sort of happenstance.

I read somewhere that Hank Williams appeared on TV with a Martin , but bought a new cheap one evry week to smash over heads of his more exuberant fans. so your fans are following in a long and proud tradition.