From your recital of facts, you had no obligation to pay support on the date of your filing (I assume that date was after your final pmt of child support in October).
The DSO document is going to look very empty.
The proof of claim protects the interest of the lender, even if the payment is made outside of the plan.
In Eastern District of MO, where I practice, only a mortgage loan payment, as a rule, could be made outside the plan, but even such a Creditor would still file a proof of claim.
Your credit report only goes back seven years on this type of claim: the Statute of Limitations ("SOL") for bringing a claim may be longer then seven years and, thus, a legitimate claim might not appear on your credit report.