Unknown characters appeared in InDesign CS6

Question

The character "Ahat" appears between the words of and Celanese in InDesign CS6. I am unable to find this character using find/change option. Even i tried to use Glyph search. But result remains "Cannot find match".
Please note that the same character has appeared while generating PDF. But unable to find and replace this character in InDesign by using the option "Text", "GREP", "Glyph" in Find/Change palette.
Help to solve this issue in InDesign.
JA

Answer 1

There is no 'character', this is a font display problem. As Peter said, it is a "character mapping" problem, but not as simple as "this character got inserted" Instead, something is going wrong in the internal character lookup table that InDesign uses to find, for example, candidates for ligatures. In essence, this looks for character combinations such as "f" and "i" and replaces them on screen only with a single ligature "fi". (Where the actual text, when copied or searched, still consists of a separate "f" and "i".)
Hence, my suggestion to switch off ligatures to test if this is the case.
If you assign another font to this text, does the problem go away?
If it does, then InDesign has a problem with this particular font. I mentioned one cause already: more than one installed font with the same name but with a different version number. To test if this is the case: check with Find Font what font file is used for this text. Remove the font file. Now InDesign should not be able to show the correct font. If it still does, it found another font file for the same font.
Option 2: the font is fine but InDesign's cached data on it got corrupted. Clear its font caches. (This involves looking for some files and deleting them. There should be instructions how to elsewhere on this forum.)
Option #3: the font file itself got corrupted. If none of the above works, deinstall the font, delete the font file, and install a fresh copy from where you got it.