It is quite clear that objects from the planes that hit the World Trade Center were recovered after the attack on 9/11. It is also clear that nobody inside the planes could have survived the crash, and few human remains were found in the aftermath. Curiously enough, though, Snopes gives a claim (marked as "undetermined") that a pair of handcuffed hands was found
atop one of the neighboring buildings.
Snopes quotes this article (originally on Newsday). The claims were apparently backed up by "police sources;" I have not been able to find those sources.
It is also said that
The hands were cataloged Friday at the medical examiner's office at 30th Street and First Avenue, which is the main facility for the painful and painstaking process of identifying the dead and establishing the cause of death.
There is a related claim that the body of a flight stewardess was found - with her hands bound. The Guardian claims
Close by was the body of a woman believed to be a stewardess, whose hands were tied with wire, Fox News said. Police could not confirm the reports.
The New York Times says
Another [rescue worker], in one of the most searing discoveries among the ruins, found the body of a flight attendant, her hands bound.
This page led me to these last two sources, and suggests that the two claims (bound severed hands and stewardess's body) could be versions of the same claim.
Wikipedia repeats the claim, but gives no new sources.
I realize that putting these sources together could make for an answer to this question of "inconclusive," but I sincerely doubt that there is no other trustworthy evidence on the issue, though I have not been able to find it.
Was a severed pair of handcuffed hands and/or a handcuffed flight stewardess's body recovered after 9/11?
I should add that I'm not skeptical about minor remains being recovered - that seems plausible. I am skeptical that handcuffed or otherwise restrained remains were found. Given the other events on-board the planes (i.e. the death of the crew in some cases), it seems odd that someone (presumably) would go to the trouble of restraining someone when knocking them out or killing them would be much simpler. It could be that one of the terrorists was restrained, but the reports seem to imply the opposite.
Admittedly, this is (educated) speculation.