The Pittsburgh Post-Gazette's Ed Bouchette confirms that this is in fact correct.
Facts: Steeler Le'Veon Bell was NOT on the team charter yesterday. He did make his way to Philly on his own. Blount was on the team charter— Ed Bouchette (@EdBouchette) August 21, 2014
However only Blount was on the teams chartered plane, Le'Veon Bell made his own way. It is as of yet unclear how Bell travelled to Philadelphia, but at least we do know that he took the initiative and went to face the music, as it were, of his own accord.
Both running backs are expected to be charged for possession of marijuana after being pulled over in Ross Township, with Bell also facing a much more serious charge of DUI. The Steelers have yet to make an official statement on the matter, and it is unclear whether Bell or Blount will play in tonight's game against the Eagles.