Even though we recover it, the Free Peoples can't use it as intended. The Rangers know that some of the palantiri are lost and possibly in the hands of enemies. It is fortunate that it is not mentioned again, since Sauron and Saruman both have access to palantiri, as does Denethor, and thus to use the one we recover would possible corrupt the user, or at the very least to inform the Enemy of our plans. Remember, Aragorn was only able to use the Orthanc palantir because he was of the line of the Kings of Numenor, with elves as ancestors, and even then it taxed his strength of will.
Narlinde, level 100 Minstrel, Rank 11, Member of Trucido ~ Windfola