If they had the Inmarsat ping, and another satellite in a different orbit recorded the same ping, that would help.
USA-223, aka NROL-32, is a geosynchronous signals intelligence satellite launched in 2010, now located at 100.9E. It is reported, by the head of the NRO, to be the "largest" satellite ever launched. It is understood that "largest" in his terms refers to the size of the associated antenna, which is estimated to be roughly 100m in diameter. USA-202, another Orion class sig int satellite launched in 2009, is geosynch at 44E.
Both these bird, was well as some older satellites which may no longer be functional, would be able to see the region in question and, as others have alluded to, be able to detect and localize Inmarsat signals. As "national assets", their involvement would not be disclosed but I'm reading something into the White House press officer's statements last week as suggesting the call on what role they could play was Obama's, as CINC.