I’ll bet that house had a very elaborate and top of the line security system. Rush was one of the Lib’s main enemies for decades. He probably spared no expense trying to keep himself and his wife safe. That includes any parking garage where the cars would be left at night. He may have even had what is sometimes called a “Panic Room”; where you quietly go if you know an intruder has entered your home.
He had a separate building (across the street or down the street) where all the mail went & was opened & checked. I heard this when he was talking about something special he had received - guy at mail facility called him to tell him about it. I’m sure he had layers of security & his mail arrangement was part of it.