Questions about HashMap's get_key_value

So I'm doing a silly thingy, with a HashMap keys of Vectors of references. I probably shouldn't, but am. During the program I wanted to get user input, find the key in the hashmap that matches, and store a reference to said key. It'd be lifetime bounded to the hashmap. I read the documentation for get_key_value, and it seemed to imply that it could be used for getting a reference to the key that the hashmap owned. But I ran into borrow checker issues. A stripped down (and now somewhat silly) e...