Did you check the car with its wheels jacked up and running or while idling?
A minor leakage in engine bay can be easily evaporated by the heat and becomes pretty hard to diagnose. It may not even come up in ordinary idle mode. On the other hand a sudden surge in fuel lines, like one caused by loading/unloading of engine i.e acceleration or deceleration, can cause just the problem, so I'd suggest to jack it up and check again. Check the FI system for any signs and rubber hoses for suspicious cracks.
It should help to use some nonflammable foam to spray on the lines, to detect minor leakage. I think it is best to use one of those little Rs-300 fire extinguisher spray cans for the job, and it's good to keep one in the car anyway.
Good luck.
P.S. Keep an eye on any loose/short circuiting wire or other fire starting points, and get them fixed immediately.