I didn't respond to that guy's post because it was clearly false.
There were plenty of body parts found during the cleanup after the terrorist attack on the twin towers. As to the claim no jet parts were found:
As the 21st anniversary of 9/11 was observed on Sunday, an old, false claim reemerged on social media saying no airplane debris was found at the Pentagon after the building was attacked.
apnews.com
A Facebook post claims that “zero plane parts” were found at the 9/11 crash sites. This isn’t true.
fullfact.org
This line of discussion is stale and uninteresting. They believe and no amount of fact checking or discussion can shake their false conspiracy theory.