If something is missing from the sort order, it sorts into the wrong
place (the end of the sorting list) but it is plainly visible. (When
interlinearizing the character will be treated as punctuation and
discarded from the parsed form of the data, but that is a different
matter -- the unparsed line still shows it.)
When something disappears altogether, it is most likely that you are
trying to display non-Unicode data as Unicode. The result is an
invalid Unicode sequence which is not displayed. Try turning off the
UTF-8 setting and see if your characters appear.
Toolbox Support