I am the health and safety coordinator at a building supply / truss plant in Canada. I don't know how well you know the management at your building supply, but it would not hurt to drop a few hints.
1) Fire extinguishers in forklifts are mandatory in Canada, and highly encouraged in the United States.
2) While in this instance the gasoline was yours, I would think that most building supply stores handle enough hazardous materials, that the warehouse staff should have spill kits available and be trained in how to use them.
3) Their emergency plan should have been initiated, and the building should have been cleared.
4) There should be a S.O.P. for loading and unloading customer vehicles. There are all sorts of potential risks present.