Not to wish ill on anyone, but they should have had insurance.
In terms of what to do next, perhaps rent a suitable premises and run their business from the new location (possibly leasing equipment, as necessary).
Do they own the actual property and if so, is it debt free ? If so, there may be a chance of getting someone to lend money to reinstate the property, in return for security over the site and new building to be constructed thereon. That said, if the business was struggling, it may not qualify for a loan but a deal with a private investor might be achievable or else, a sale and leaseback (post reconstruction) type arrangement.