"If I wanted to talk about feelings, I would have called Oprah," Frank told The Hill on Wednesday when asked his feelings about being overlooked for the appointment.
Frank had publicly lobbied Massachusetts Gov. Deval Patrick (D) to name him to the Senate on an interim basis after President Obama nominated Sen. John Kerry (D) to be secretary of State.
Frank, who retired from Congress earlier this month, told MSNBC in early January that he wanted the appointment so that he could serve during negotiations on the debt ceiling and sequester.
Instead, Patrick named his former chief of staff, William “Mo” Cowan to be Massachusetts' placeholder senator until a special election is held in June.
Frank, who served for three decades in the House, said he wasn't concerned that Massachusetts would lack seniority in the Senate with only Cowan and freshman Sen. Elizabeth Warren (D) currently representing the state.
He noted that the two senators "have a very good congressional delegation to work with."
Frank said that while he didn't know Cowan well, he was confident the new senator would support Obama's agenda. He urged Cowan to stand up against Republicans.
"Substance is important. Increasing the debt limit is not a favor that the Republicans do for us. And particularly, the Republicans are every bit as responsible for the debt we have to pay as the Democrats, maybe even more so," Frank said.