We had just entered the left-hand lane of the westbound trestle east of Everett - this is a looong pair of bridges over a tidal slough - one bridge each for eastbound and westbound traffic.
Suddenly there was a powerful vibration from the rear of the Suburban. My mind, not yet working at full speed, started to form the thought that we were having a blowout. And then with a *crunch*, the left rear of the vehicle dropped to the pavement, convincing me that we were now riding on the rim. The vehicle lurched to the right, but despite the heavy traffic, the vehicle over there managed to avoid us - no contact was made. Just as I got the Suburban back into our lane, we were passed by our wheel and tire, still going 60 mph; it rapidly disappeared out of sight ahead. OK then, no blowout - we lost a wheel! Thankfully, since the trestle is a divided roadway, the wheel could not encounter oncoming traffic. If it had, there very probably would have been serious injury or death.
The heavy traffic really saved us. Everyone around us saw what was happening and kept clear. Those too far back to see us were confronted with a sea of brake lites, and so they slowed down too. There were no accidents.
Stationary in the left-hand lane, I got out and looked - yep, no wheel on the left rear. The brake drum was still on the hub, and had acted as a sort-of lumpy cast iron wheel during the decelleration, minimizing damage and allowing the vehicle to decelerate more or less in a straight line.
Soon a very courteous state policeman pulled up behind us and turned on his flashers, which helped to warn the traffic. And then an Incident Response vehicle pulled up. I briefly talked to them, and then walked ahead along the narrow walkway to see if I could retrieve the wheel so we could get the vehicle off the bridge. Sadly, it was nowhere in sight. But just as I got back to all the flashing lites, a stranger pulled up behind the Incident Response vehicle - he had my wheel in his back seat! And in order to retrieve it and get back onto the westbound trestle, he had to have driven perhaps 15 miles! He dropped it off and then disappeared - what an amazing Good Samaritan! I should add that the Suburban is a *big* vehicle - the tires and wheels are big and heavy. And yet he had managed to wrestle it into his back seat. Again, amazing.
The Incident Response guy jacked up the rear and we put the wheel back on, using one lug nut stolen from each of the remaining 3 wheels, and we got the vehicle off of the trestle.
Just the week before, we had dropped $1k on new tires - so it was back to that tire store that we got towed. The manager was visibly chagrined, and took very good personal care of us, including even springing for our dinner. As Jane said, "This was our lucky day, and so it was your lucky day!".