Neither have I. The number of people who have encountered such events is probably close to negligible.

However I bet there is a good chance that will not be the case for self-driving cars. The reason is simple: human brains are slow.

When caught by surprise by an unexpected sudden obstacle a human driver takes about a second to realize something must be done and decide on braking or swerving in the fastest path, where the brain bypasses conscious decision making and uses the lower level fight or flight system. (Then another maybe 0.2 second to actually start swerving or 0.4 seconds to actually start pressing the brake--brake takes longer because of the need to move the foot to the brake pedal whereas the hands should already be on the steering wheel).

If they try to actually evaluate whether swerving or braking is the better choice before acting add another 0.3 to 0.5 seconds. That brings it up to around 1.6 to 2 seconds before they start actually acting, which most of the time is going to too late to actually affect things. Hence essentially no trolly problems for human drivers.

Compare to a self-driving car. The can detect the obstacle and predict the collision, and do a cycle of path planning before the retina has finished registering the obstacle and started transmitting that information to the brain.

By the time a human reaches the point where the brain knows something bad is happening and is starting to deal with it the self-driving car has had time to calculate numerous alternative trajectories to try to get around the object or stop before reaching it, taking into account predictions where all surrounding objects will move during the next few seconds, and calculate the damages for the trajectories that cannot avoid hitting something.