Is having contact information on my work important?

Is having contact information on my work important?

Randy Stradley (Senior Editor of Dark Horse Comics) gives expert video advice on: How can an artist submit his work to you?; What is the ideal artist portfolio?; Do you prefer reviewing original or photocopies? and more...

It should be on everything that they leave with me. I've had it happen in the past where somebody's given me great samples and I get back to the office and I realise they don't have their name, phone number, email address or anything on the pages. Therefore, I have no way to know who that person is and no way to contact them. I've had great samples in the past for somebody who didn't get a job because I didn't know who they were.