Lessee, I've seen the Ion Storm and Fire Storm events, plus I've had several stars go bye-bye. I've also returned to distant systems after awhile and found them . . . gone.
I've also seen one called the Spacial Anomoly. It picks one of your ships and flings it . . . someplace. It has the annoying side-effect of breaking up the fleet the ship belonged to, even when leaving the rest of the fleet in place (so much for their fleet experience!
).
I've also had a neutral empire's ship pop into my system spontaneously. I can only assume they've been struck by the same event.