Would a charge of felony possession of a firearm cause him to return to prison?

Would a charge of felon possessing a firearm have to be dismissed if the firearms were his dads and taken from his dad's house and he was in jail when they took them? I believe the police in this county to be corrupt and looking for a way to put him in jail. He has a felony from 2002 and successfully completed the sentence of jail time and remaining 10 year probation. Hasn't been in trouble since and was recently set up by a friend with a stolen trailer. This trailer was brought to him and when he left with it was surrounded by 12 cops. It had a tracker on it but the newspaper said a routine traffic stop for no license plates. Then they say they had probable cause to get search warrant to his dad's house while he was in jail they kicked in door with another 8 cop cars present with warrant specifically looking for any drugs or packaging material. They didn't find anything like that but took 20 firearms legally purchased and registered to his dad who collects them. Most of never been shot.