The statute (FDCPA 809(b)) does not require that a findng of validity made by a debt collector and conveyed to the consumer must "prove" the legitimacy of the debt. Case law interpreting the degree to which validation requires any supporting documentation or proofs generally holds that a statement of finding is adequate. However there are cases where the judge has interpreted that some degree of documentation is required. In the end, what is or is not adequate validation is what the judge interprets the statute to require.
In most federal jurisdictions, no requirement for supporting documentation is the standard, and their finding would not require a signed contract.
HOwever, it also depends upon your state of residence, as some states have enacted enhanced debt collection practices statutes that do include additonal requirments. It is not a simple answer of yes or no.
Also, be aware that FDCPA 809(b) imposes no period for, or even any requirement to, send any validation.
A DV request, if timely, only imposes a cease collection bar on the debt collector, which remains in effect until they choose to send validation. If you consider validation to be inadequate, that means that you consider them to remain under a cease collection bar, and not that they are required to then send whatever you deem to be necessary.
Finally, FDCPA 809(b) requires that the consumer assert that the debt is not valid, in whole or in part.
If you acknowledge that the debt is valid, there really is no assertion that it is not.
