Don't worry we LOVE newbies on Trulia! It is helpful to give as many specifics as you can when asking a question so that the folks who respond can be sure they are giving you the right information. If you can reference property addresses and the source of the information you are referencing it helps us to make an informed assessment of your question and give you our best answers without having to ask you questions in response to your question...does that help?
Anyway, Pacita has given you some general info on what COULD have happened in the case of the properties you talked about in SF and Oakland (94601). Best of luck to you as a home buyer/seller and Trulia participant!