I'm not positive who's supplying the figure of $20,000, though I'd guess it might be RealtyTrac. There have been many, many threads here about the erroneous, misleading, and incorrect data provided by that company.
If the property is even for sale (and lots of so-called foreclosures on RealtyTrac are not for sale), just find any real estate web site serving San Francisco. Virtually all have some sort of form that allows you to search the MLS. You have the address (though it appears you left off the street number above), so that should be sufficient. If you can't find it, it isn't for sale. However, you can ask a Realtor what the status of the property is, even if it's not on the MLS.
Hope that helps.... more