Is there a problem using punctuation in searches? I tried to search for "Lord's day" both with and without the quotation marks. I get no "hits." But the expression exists right there in Rev. 1:10. Somehow it is invisible to the Search function.

Sometimes different publishers of the text have used a different character there in "Lord's day", it could be a ` ' ’. I know of course it is an issue if you search multiple Bibles with boolean search. You can have a look in the search window's virtual keyboard, which lists all the characters used in that module.

or in some cases it could be that Lord's is shown as LORD's or something similar.

You could try a search like this boolean one

Lord nearw1 s nearw1 day

and check the options "whole words only" "ignore case and diacritics"