I have a policy of simply ignoring these.
That's rarely the case. Debt collection agencies will absolutely hound you and your relatives, damn the laws, to try and milk value from you, for quite some time. They will then go to conferences and brag about how they have tricked people into claiming debts, the ways they have harassed people, and other atrocious things.
My friend has told me that on occasion the debt collection company will reach out to the original owners of the debt and request additional information, but seldom get a response.
Anyone reading this, it is absolutely in your best interest to fight any debt, no matter if you believe you owe it or not. Nothing changes if you fight it and they have sufficient proof. Best case scenario is they wipe it from your credit report.
If you’ve already began making payments then you’re SOL, as making payments is considered ownership of the debt in question.