I watched a new user struggle with this the other day. I told her a person/user to search for in response to a question she had. She typed the name in the popup search and intuitively hit ‘enter’ very quickly before the pop-up results were returned.
I said, “hmm… guess users aren’t returned on this page…try that again, but don’t hit enter right away”.
Then, when she clicked on the search icon again, the cursor just went to the main search box… which was unexpected (as @pfaffman notes above).
I had to guide her to go back to the home page, then click the search icon, type the user name, but do not click enter immediately, and voila, the user we wanted to find was right there…