There's a reason the Detroit Lions did not announce anything about the . They didn't want to jump the gun in case something came up before all of the physicals had been passed and everything was official. trade
As it turns out, that was a good decision, because Adam Schefter is reporting that something has in fact come up. According to Schefter, the trade has been voided because Jerome Harrison "had health issues." Whether or not that means Harrison failed his physical I'm not sure, but it really doesn't matter. What does matter is Harrison is still a Lion and Brown is still an Eagle.
This puts the Lions in a tough spot. It's going to be pretty awkward for Harrison to return to a team that tried to trade him, especially considering his health was the reason the deal didn't go through. The Lions wanted to upgrade the running back position by adding Brown, and now they're stuck with an apparently unhealthy Harrison.
If the deal had been voided in advance of the trade deadline, the Lions could have tried to work out a different deal. Since the trade deadline has passed, the Lions are stuck with Maurice Morris, Keiland Williams, Jahvid Best and Harrison as their running backs unless they release one of them and bring in a free agent.