I have a question for you. Did you receive the loan from the same company? If they were both originated, and funded by the same company -- chances are, they were actually sold together, to the same Investor. So, if your first mortgage is owned by something like ABC Mortgage Trust 2006-2, chances are the same loan, is with the same investor, and serviced by the same company.
One big clue... may also be the county records. I'm not sure what county, or state that you are in, but in many parts of the country, for free, you can find the register of deeds online. You can then search your name, or the borrower's name, and find copies of the original mortgage liens that were recorded.
Once you are looking at it, sometimes, you'll see something like an Assignment of Mortgage. There will be a Dollar Amount Listed, the Original Date of the Loan, and who the new entity is. This will likely have an address, which you can mash into google, and sometimes find a phone number for.
Another idea -- if the loan was a part of something called MERS, which you'll see on the page of the document if it's there, is to go onto to the MERS website, and type in the ID Number. This will list the last known servicer, address, and phone number.
Once again -- this can usually be done online, but if it can't, you can go in person and purchase printed copies, of the documents and original deed to your home. But this is what I would start with.
If it proves fruitless -- come back, and I'll give you a few other methods to try. But, having a copy of the original lien, would really help.