We ain't made of what we thought

Given that the age of the universe since the Big Bang has been estimated to be about 13.8 billion years, and that our sun is about 4.5 billion years old, with another 4.5 to go, and also that super giant stars live a shorter lifespan, there were probably many, many supernovae before the sun was even born. So pretty much everything we find on earth was already around somewhere and may not have been swept into a galaxy yet.