It sounds like you were not in the house for some time, they purchased the home, believed it was abandoned, and went to secure it. When they got there they saw your boxes, looked in them to see if they were full of junk you left behind or your actual belongings. They determined it was your actual belongings, and they called you to let you know what happened and they gave you a way to get into the house while still keeping your belongings secure via their new lock.

Do you have any evidence that this is not what happened? That they actually stole or damaged your goods?