Yes. Abolutely. Use it. Sometimes you'll request validation from the collector or creditor and they'll admit that you don't owe the debt or that they can't or won't validate it.
Put that admission in as an enclosure to your credit report dispute (do it in paper and use the mail so you can sue later if need be!) as more evidence that either:
a) the collector/creditor investigated your debt and it isn't valid or
b) that the collector/creditor didn't investigate your debt even though you provided some reason to dispute it.
If you have any other questions please don't hesitate to contact me online or call me directly at 415.802.0137.