the weather on the east coast is kinda atrocious right now, I am sure the pilot MUST have given a reason why the plane was brought back. They don't return the plane back to the gate without some kind of explanation. My guess would be an air traffic delay caused by the weather the midwest and north east coast are experiencing. And if your friend is leaving out of EWR/JFk/LGA then its definitely weather. The flight be listed as in range (pushed out, on the tarmac, etc) because it's presumed it will take off at some point when there is an opening. Again the weather on the east coast is extremely bad and all the airlines are effected by this. You can check all this out over at
www.flightstats.com and then relay the info there to your friend if the airline isn't giving out information. Hope this helps.