The police handcuffed Zimmerman and put him in the squad car to take to the police station. Technically not an arrest as they didn’t say “You are under arrest” and read him his rights.
They took his gun at the seen and still have it for evidence.
seen = scene
IF, the report you linked is true, I would be wrong about police returning the gun, BUT it says “The gun is now in the possession of authorities, officially part of the evidence in the case.”
There is no reference to how they know this. A link to the official who supposedly said this would be helpful.
The horses mouth so to speak. We know the media lies. Trust but verify.