You are all off target on this one...
The minute he said no to the search because he had done nothing wrong, they simply wanted to show him that they were in charge and would /can enter in through the back door.
Your Attitude triggered this arrest. ... I have seen this many times before. You will get your weapon back but not until your attorney file motions which will cost you more money and that's exactly what they want plus that arrest is in the system for all future officers to see and explore that same route if they so desire.
Don't ever make yourself out as a lawyer knowing your rights and all the laws before LEO BECAUSE they will show you exactly how they can operate having what they consider as extreme state power.
Next time you are ask for a search simple answer is no, no more conversation is needed.
Your answer was KNOW not No.... as in, I know all my rights!