So the owner chose to not press charges in exchange for getting the firearms back immediately. If he had pressed charges it may be a year or more before he gets the firearms back. So there is the rest of the story.
Photos and videos are used ALL THE TIME as evidence in court and works just fine. The evidence can be examined, authenticated, whatever to make the case.
Why, in this modern age, do we have to keep someone's property to convict? Take video from all sides, close-ups, stills, glamor shots ... whatever is needed. But there is no reason to keep the property.
Property can even be tagged, marked or otherwise identified by serial numbers, etc. If it's needed in court, that's all that's nevessary to know this was the exact property involved.
Sometimes I think our system is designed to be cumbersome and burdensome for the state and victims on purpose!