For what it's worth, there are many cases even in the natural language where ' is not supposed to have a "closing" counterpart - indeed, the "it's" in this very sentence is one such example. Then you have the use of ' to denote feet and minutes of arc. Now, technically these are all actually different symbols, with their own Unicode codepoints etc - but in practice, people use ' for all of them, and it doesn't seem to be confusing anyone. You could treat the ' in Rust as something along these lines.

In fairness, you should never be searching for matching apostrophe. Single quote, maybe. The fact that it's an apostrophe should also trigger that it might have something to do with possession... (or that something was omitted).