Why did my steering wheel lock come on while driving my car?

The ignition lock includes the steering wheel lock. It's possible that it just needs lubrication, or that the lock part has broken. In either case, taking the covers off the steering column sounds like your next move.

you removed the switch, but what about the lock cylinder the key goes into?

Has it thrown or broken the belt?
When you say locked do you mean real hard to turn or the locking pin has engaged?

wiggle the steering wheel. this frees up the steering lock pawl, insided. all cars. if parked on a hill , against a curb 10x worse
read the operators guide, it covers this , in step one, driving.

it the key swich

I don't know for a fact but this seems very odd to me that your vehicle would not have a steering wheel lock. Further, it is more odd that the wheel would lock unexpectedly while driving. Obviously, you cannot drive it in this condition. I recommend you take the car to the Ford Dealer and have them repair it even if it means replacing the steering column. You certainly don't want the thing locking up while you are driving ... all sorts of terrible pictures come to my mind ... running into oncoming traffic ... off the right hand side of the road ... off the bridge into the valley below ... into a group of chldren waiting for the bus ...

Please get this fixed as soon as you can.

Sounds like the steering wheel is locked.
Grasp the steering wheel with your left hand and wriggle the steering wheel whilst at the same time gently turn the ignition lock with the key. (For left hand drive)

try switching out the coulmn lock and check steering box and linkage

When they did the alignment it's possible that they used a tool that locks the steering wheel straight while it's on the alignment rack.If they put too much pressure on the wheel when they used the steering wheel seat lock tool it may have stressed you tilt lock mech causing it not to lock where you want it.Hope this helps

Although the car is not in front of me, it sounds like when you park ( is this parallel parking ? ) your steering wheel is turned hard to the left or right, which creates extreme pressure on the steering wheel lock. In order to help overcome this problem, you must "armstrong" the steering wheel in the same direction the front wheels are turned. Locking up on the freeway with this same issue. Highly unlikely.