I had a close call like that driving down 80 in the 914 from Oakland to Fremont.
The freeway was pretty empty (Sunday morning) and a SUV that was a couple of hundred feet ahead lost its spare tire that was bolted under the car.
I saw it come down and got stuck under the car for a second and then popped out and went way up in the air.
I slowed down and the tire came back down right in front of me and luckily bounced again and jumped right over my head.
There was nobody close behind me and i watched the wheel bounce a few more times and come to rest in the right lane. Hopefully nobody got hurt running into that.
The whole thing was so surreal, i'm sure it only took seconds but it felt like a slow motion movie.