What happened to the Resurrection Item? In the Sword Art Online anime, after getting the Resurrection Item Kirito gives it to Klein, as Kirito wanted it to bring Sachi back to life, but for it to work it had to be administered within 10 seconds.

Do they ever explain what happened to the item after that; the anime doesn't show if Klein ever used it or not?
This item was not mentioned after it's introduction.

During that introduction Klein was given it with the instruction to use it on the next teammate who dies in front of him.

During the final battle he has every motivation and opportunity to use it as the wife of the man who gave it to him has died right in front of him! He does not use it here. It is unreasonable to think he would not use it under that circumstance.

An object like that would not be disposed of carelessly.

This yields two possible answers: he followed the instructions given to him (Very possible) or he gave/sold it to someone else and they used it, sold it again, or retained it until it did not matter anymore.

In either case, this is neither a plot hole nor a deep mystery as it was a relatively minor plot element, we were told exactly how he should use this consummable, and, if he did so properly, it would not have been a large enough plot point to warrent it being shown.  I doubt it would retain its value by the later stories so it doesn't even matter if it wasn't used by a purchaser by the end of SAO.