What happens now is what should have been spelled out in the contract. It will really depend on the insurance policy if your gear is going to be covered. Most policies will NOT automatically cover another vendors gear that is left there. If he says that the gear is his to get the insurance money, that is insurance fraud, and I wouldn't want to be anywhere near that.
What happens now is you should immediately put together a contract for your services. It can be an open ended agreement that can be cancelled by either party at any time. Pubs are notorious for not wanting to sign agreements, so they have flexibility to change at will. Taking that into consideration in the contract eliminates that concern. The contract needs to specify liability for both you and them.
As far as the gear goes, without a contract, I'm not sure that you could force the venue to be liable. YOU should have insurance on your gear for that purpose. Make sure the policy actually covers what you plan to do. Leaving gear unattended is a different policy than if you are protecting the gear while it is in your possession.
Suck that this happened to you, but take it as a learning lesson and don't let it happen again!