These shoulder bolts can come from several places on your car.
One would be a Seat belt - but those have a much bigger shoulder and thread size - this one is not that size you'd find in the anchor bolt for the Seat belt - nor in the harness and seat belt buckle clip.
Since you found this on the floor of the Garage - if it came from the exterior, you'd also know by how the vehicle rattles and has loose trim - so I don't think it's related to the engine - it may have com e from one point in the car I've deal with this before in my own Ford.
How did it wind up on the Garage floor? It may have come off in your lap and you simply tipped it out of the car onto the floor.
The steering column - there are several types of bolts that hold the column to the crossbrace and crash member - it would be under and behind the trim. The purpose of the bolt is to provide stability and anchor the column axis, while letting the steering wheel tilt and slide to fit the users' reach and grip for the steering wheel. So that shoulder just acts as a guide to let the column slide yet hold the assembly to the braces.
Steering Column Bolt - Ford (W709942-S424)
See if a dealer can identify this.