Oh, I get it. YOU are the creditor. Well, never mind my first answer.
Except the part about it having no effect on the Fico score. You just bought a second position lien. You did not agree to guarantee the first mortgage for the debtor, did you?
Your Fico score is tied to your obligations as a debtor. You are the creditor in the situation you described.
A debtor is someone who owes money. A creditor is someone to whom the money is owed.
So my answer is still the same for a different reason: This should not affect your Fico score at all.
Please come back to this thread after all this is sorted out for you, to tell us Trulia readers if you got anything back on your investment at that auction, or if it is all money washed away under the bridge.