The liability may fall primarily on the venue, but if the evidence is that the band members caused the damage/injury, the venue's insurers are likely to want to join the band in any litigation to seek an indemnity against the band. Band members may disappear into the night, but normally the band 'leader' or agent has left his/her contact details. Going to Court is expensive and time consuming and being unrepresented can be very foolish if decent money is at stake, so it is advisable to have insurance, especially if this insures your gear and has legal expenses insurance as part of it.