Anything with an ’ in it doesn’t tend to appear. Not very helpful if you’re using contractions and you use the wrong ones. Suddenly realizing it many pages later. Or writing stories with fancy Alien names that are hyphenated with apostrophes. But you spell it wrong in one or two places.
Probably your problem arises from AutoCorrection and you get apostrophes replaced by typographical font specific characters. Check Tools -> AutoCorrect -> AutoCorrect Option -> Tab: Localized Options -> Option: [x] Replace in section Single Quotesbeing active. If yes - this may be the reason, that you don’t find ' using find and replace, since they may have been replaced due to that setting (Unicode character U+0027 replaced, in my case, by U+2018, U+2019…, depending on the context, when having activated this setting), You may search using \u2018 etc, in Find&Replace dialog and having option [x] Regular expressions activated.