Shocking Surprise

I would say if the outlet is a GFCI, it is defective or mis-wired, and if not, install one.

"How they work"

The basics of GFCI are exactly what you experienced---to prevent a shock from power to ground.

They do NOT prevent a shock from a hot wire to neutral, if you are on an insulated AKA dry wood floor. The GFCI senses balance/ imbalance. When properly operating, the current flows from the hot side back to the neutral, and "is balanced." But current to ground forms an IMbalance and causes the thing to trip.

In other words when you touched the vehicle, a GFCI should have tripped. In fact, "leakage" through steel belt tires should often be enough to trip one as well, morning dew and so on