Misunderstanding of ‘invalid’.
“A prize claim shall be entered in the name of a single individual or organization. A claim may be entered in the name of an organization only if the organization is a legal entity and possesses or has applied for a federal employer’s identification number (FEIN) as issued by the Internal Revenue Service. Groups, family units, organizations, clubs, or other organizations that are not legal entities, do not possess a FEIN, or have not applied for a FEIN must designate one individual in whose name the claim will be entered.”
Face it, the lawyer screwed up (or was scamming). There are ways this could have been collected. Someone didn’t do their homework.
I'm not sure what you are referring to. The first two sentences of your cite say:
A prize claim shall be entered in the name of a single individual or organization. A claim may be entered in the name of an organization only if the organization is a legal entity and possesses or has applied for a federal employer’s identification number (FEIN) as issued by the Internal Revenue Service.
A trust is an organization. It is a legal entity, and has a Federal EIN.
The attorney was the trustee, and represented the trust. The actual winner was presumably the beneficiary. If the beneficiary instructs the trustee to not reveal his identity, then the attorney has no choice -- or he faces disbarment.