As previously reported, Locklear was arrested on February 25 after authorities responded to a 911 call about a domestic disturbance.
Locklear told deputies she would "shoot them if they ever came to her house again".
Locklear resisted arrest, and was also booked for allegedly pushing and kicking the deputies.
She was arrested on a felony domestic violence charge and three counts of misdemeanor battery of an officer.
Law enforcement sources tell TMZ, police went to Heather's Thousand Oaks home armed with a search warrant and went inside the house and looked for the weapon for several hours.
An investigation into Locklear revealed she had a firearm registered in her name.
Cops toss Heather Locklear's home in search for a handgun she bought in the 80s but come up empty a week after she 'threatened to shoot police' during domestic violence arrest
After failing to find the handgun in the search of her home, police are said to be considering their next move.
Locklear wasn't present for the search, as sources told the website she is now being treated in a medical facility after posting $20,000 bail.
The source said the actress snapped and "attacked three of" the four officers - all in front of her "mortified" adult daughter Ava, age 20. The 56-year-old claimed she had been "battered or injured" prior to their arrival and was later transported to a hospital for evaluation "out of an abundance of cation".
Over the past few months, Locklear has appeared eager to put what she called her "drama-filled past" behind her.
Locklear's first court appearance is scheduled for March 13, while Heisser's DUI hearing is set for April.
Following the arrest, the actress was released on bail.