How long did the police search for the murder weapon?

I scoured through this story in an attempt to find an exact amount of time that the police spent searching for the murder weapon.  There is no stated amount of time that the police spent looking for the murder weapon.  I can put forth a fairly accurate guess though.  

The story says that Mary Maloney was waiting for Patrick to get home.  She looked at the clock and it said 4:50.  

When the clock said ten minutes to five, she began to listen, and a few moments later, punctually as always, she heard the tires on the gravel outside, and the car door slamming, the footsteps passing the window, the key turning in the lock. She laid aside her sewing, stood up, and went forward to kiss him as he came in.

For the sake of simplicity, let's round the time off.  Patrick came home at 5 in the evening.  He comes in the door.  Sits down.  Finishes his first drink really quickly.  Gets a second drink.  Then he begins telling Mary that he is leaving her, which didn't take long. 

And he told her. It didn’t take long, four or five minutes at most, and she say very still through it all, watching him with a kind of dazed horror as he went further and further away from her with each word.

I figure that it is probably 5:15 at the latest.  Mary operates in a daze for a bit until Patrick tells her he is going out again.  Then she clubs him over the head with the leg of lamb and kills him.  After that, Mary cleans herself up, rehearses her grocery store exchange with Sam, and leaves for the grocery store.  The text tells readers that it was just before 6 o'clock at this point.  

It wasn’t six o’clock yet and the lights were still on in the grocery shop.

Mary gets the groceries that she needs and heads home.  She is "shocked" to see her husband dead on the floor, so she calls the police. The police "came very quickly."  I figure 6:30 at the earliest.  From that point forward, I have to assume that the police began to look for potential murder weapons.  

At 9 that night, Mary offered to feed the remaining officers.  They all sat down to eat the murderous leg of lamb.  It's possible that the police kept searching after their meal, but the story ends.  By my calculations, the police searched for the murder weapon for about two and a half hours.