There are many homes that still have title held by an owner who has long since moved out due to the fact that they have received a notice of default and believed that the bank would be completing the "Foreclosure", soon.
Read here about my article on the moratoriums prevent banks from foreclosing on homeowners with certain types of loans: http://janegrant.wordpress.com/2009/06/07/temecula-real-esta
Check the public records--the tax records. Any deed transfers will be shown there. It'll have the investor's name as well as an address (for tax billing).
Sounds as if the investor bought the property at a tax auction or similar. Different jurisdictions handle that in different ways. Some simply sell the properties for the amount of the unpaid taxes. Some conduct an auction. In some areas, there's a right of redemption--the previous owner can reclaim the property by paying the taxes, plus interest. In other cases, there's no right of redemption.
So you check the tax records. You'll find the investor's name and mailing address. If that isn't sufficient, do an online search. If that isn't sufficient, contact a local real estate investing club. (Go to http://www.creonline.com and look for the state-by-state club listings.) It's likely the investor is active in one of the local clubs.
Hope that helps.