Landlord Entered Home With A Gun And Changed Lock

I am helping my MIL out with a situation she’s found herself in. She moved into a duplex a few months ago with the landlord on the other side of the home, the landlords girlfriend took a disliking to her and eventually it amounted to her getting a frivolous protection order against MIL. While MIL was at work, landlord entered the unit with a gun on his hip, changed the lock, and locked MIL out. She had not been served with the PO. They claimed all her items belonged to them now, and that they could take anything they wanted. Coin collection and a few hundred bucks comes up missing when I’m finally allowed to clear the place out. What should we do? MIL wants her stuff back but I’m not really sure we could prove much as she only has one photo of some of the collection, and no proof of the cash or anything. Thoughts? We also have the illegal entry on video and it is quite clear. Washington State btw