I think they were just protecting their customer. I would give the dealership your phone number and ask them to let the original owner know you would like to speak to him about the car's history.
If you have to use the brute force method, there are several reverse phonebooks on the internet and you should be able to get the number unless it is unlisted.
Do a Car Fax and have the dealer service department print out the service history on the car (they can do it while you wait or post on the forum and someone can get it for you). Good Luck