They met with staff in Kyl's office, Upton said, and McConnell was not in his office at the time of the meeting either.
The House committee approved legislation this week to nullify EPA's power to regulate greenhouse gases from power plants, refineries and other sources.
"We are just finding out what they are doing over here," Upton told reporters while en route into McConnell's office.
Senate GOP leaders want to advance the plan -- which is sponsored on the Senate side by Sen. James Inhofe (R-Okla.) -- as an amendment to small business legislation that's currently on the Senate floor.
Senate votes on the block-EPA plan appeared imminent Tuesday and Wednesday but have not occured, and plans appear unsettled after Wednesday's vote didn't materialize.
Key GOP supporters of the plan have accused Democrats of backing off because they fear a bad outcome, but Democrats say that's not true.
The amendment is highly unlikely to win the 60 Senate votes needed for adoption, but a clear majority vote would nonetheless be a political setback for advocates of EPA emissions rules.
Sen. Joe Manchin (D-W.Va.) is a co-sponsor of Inhofe's plan, and some other centrist and politically vulnerable Democrats may back it too.
This post was updated at 6:58 p.m.