There were all sorts of exaggerated performance technology demonstrators before the war, offered by questionable companies (*coff coff* Brewster Aeronautics *coff coff*).
In this case, the back story practically writes itself - the prototype gets driven around LA to gather press attention and investors.
As soon as word of Pearl Harbor reaches LA, the company valiantly offers it's services to protect the city. During the night of 24-25 February 1942, the crew goes into action but the contraption disassembles itself. The scrappers show up two days later.
No one ever speaks of it again.
