Sure, easy for them

Rico says it would be funnier if it weren't so stupid, but TPM has a column by Evan McMorris-Santoro about the latest (but not the last, Rico predicts) goof by the Republicans in Congress:

Call it a stumble out of the gate. Or a failure to find the gate entirely. Veteran Representative Pete Sessions, a Republican from Texas, and freshman Representative Mike Fitzpatrick, a Republican from Pennsylvania, failed to make the official swearing in ceremony yesterday, a violation of the Constitution that has sent Republicans scrambling and briefly brought an end to the new majority's push to repeal the health care reform law.
While the rest of the House was being made official in the chamber, Sessions and Fitzpatrick were outside the room at an event for Fitzpatrick supporters. The pair reportedly took their oath to a televised image from inside the chamber.
Freshly-minted House Rules Committee chair David Dreier, a Republican from California, had to recess hearings on repealing the health care law after he learned that Sessions, a member of the committee, was not in fact a Constitutionally-valid member of the 112th Congress. Sessions had been casting votes all day like the duly-sworn members on the committee.
Dreier spokesperson Jo Maney told TPM that she "didn't know it happened" that Sessions wasn't sworn in, but after Dreier found out about it, he recessed the hearing to sort out the mess.
Sessions has now been officially sworn in as required by the Constitution, Maney said. The same goes for Fitzpatrick, she said, though that's of less concern to the health care repeal as he's not a member of the Rules Committee like Sessions is. But the failure to be sworn in could mean the rules package the House passed on Wednesday doesn't count. The action is now behind the scenes, as Speaker John Boehner tries to persuade House Minority Leader Nancy Pelosi to agree to a unanimous consent decree that would make all the work Sessions and Fitzpatrick did over the past day count retroactively. Pelosi's office did not immediately respond to a request for comment on how that process is going.
The foul-up by Fitzpatrick and Sessions, both of whom have been sworn in to Congress before (Fitzpatrick defeated Democratic Representative Patrick Murphy, who defeated Fitzpatrick in 2006) is simple: the pair were not in the House chamber when the rest of the House was sworn in. Sessions' office sent over this statement explaining the situation:

"During the swearing in of the 112th Congress, Congressman Sessions stated the oath publicly in the Capitol but was not on the House floor. To ensure that all constitutional and House requirements are fulfilled, Congressman Sessions officially took the oath of office this afternoon from the House floor. Public records and votes will be adjusted accordingly."

Where was Sessions? He was with Fitzpatrick at an event for Fitzpatrick supporters held in the Capitol Visitors Center, a massive underground complex attached to the Capitol Building.
From the Bucks County, Pennsylvania Courier Times, which covered the event:

Wednesday, a sea of about 500 supporters overwhelmed a large room in the Capitol and caught a break when the Bucks County native took the oath of office in front of them rather than on the House floor.
"That wasn't planned. It just worked out that way," said Fitzpatrick, who happened to be introducing Texas Congressman Pete Sessions while glad-handing his supporters in the Capitol Visitor Center that he secured for them when the House swearing in began.

The story has an accompanying photo of Sessions and Fitzpatrick taking their oath of office in the auditorium, where the event was being televised live.
Sessions was chair of the NRCC in 2010, charged with racking up victories like the Fitzpatrick's on behalf of the GOP. By stopping off to take a victory lap on the day the 112th Congress he helped craft began, it seems Sessions (temporarily) left himself out of it.