1987 Toyota Camry oil change mystery

I took my 87 camry wagon for an oil change. After driving about 330 hwy miles the engine died. There was less than 1/2 cup of oil in the engine when drained and no signs of oil leaks. The engine had less than 80,000 original miles and was in excellent condition. The oil changer says that without oil, the car would not have made it out of the parking lot. My question is could there have been enough residual oil int the engine to keep it running for a while? The only apparent explanation is that they did not put oil bakc into the engine, but they argue that the car would not run at all without oil. The light came on when I picked it up, but it went out, so I did not take ite back right away.