Reading through the history of the case[1], it looks like the District Court ruled that the Federal TSA officers involved were entitled to qualified immunity under the Federal Tort Claims Act. The reasoning was that the TSA followed appropriated procedures and wasn't responsible for the longer (few hour) detention by the Philly Police. In my opinion, that seems reasonable. The TSA only detained him for 15-30 mins to question him about the cards, then turned him over the the state police.
After that ruling, the parties settled. I'm not sure why the case wasn't pursued further against the Philly Police. It could be that the case wasn't likely to succeed under Pennsylvania law, or maybe the ACLU wasn't interested in continuing to pursue it, since a Pennsylvania precedent wouldn't be a "worthwhile" expenditure of ACLU resources.