If you type in the name of a contact(s) that you are searching for in all lowercase letters in the Messages pane, the search returns no contacts because the contact(s) you were searching for probably had a capital letter to start their name(s).
i.e. I search for "nathan", but "No results" is returned in the contact column. But if I search for "Nathan" or "athan" the contact I'm searching for appears like they're supposed to.
i.e. I search for "nathan", but "No results" is returned in the contact column. But if I search for "Nathan" or "athan" the contact I'm searching for appears like they're supposed to.