Hidden in the "Messages" app? Not that I've ever seen. There's not really a place to hide contacts. You can search the message field as you type letters, and see what numbers and/or email addresses show. Most people don't think to delete the recents. See the screenshot. Or, one can create a contact. Then scroll down to "Share Contact" and email the contact to themselves. Then from the inbox, they can drop it in a folder to hide it. Then go back to contacts and delete the contact info card.