A security guard was on duty at the time of the theft, police have confirmed.
Mr Knowles refused to comment if police were embarrassed by the theft just three days out from the tournament opening in the city.
He referred further questions to Cricket World Cup organisers.
Police also said today that streakers could be fined $5000 or even jailed if they invade the pitch at the ICC Cricket World Cup 2015.
Superintendent Sandra Manderson, national commander of the police's Cricket World Cup Operation, said officers would work with security staff at match venues to ensure a safe and secure environment.
"We will have no tolerance of any individual that enters the field of play, without authority," she said.
Anyone convicted of invading the pitch is liable to imprisonment for a term up to three months or a fine not exceeding $5000.
Under the Major Events Management Act 2007 there are increased penalties for the offence of invading the playing surface or throwing objects onto the field of play at major sporting events.
Superintendent Manderson said the public needed to play their part in hosting the tournament by "providing a warm and friendly welcome to our international guests".
Mr Knowles said there would be a visible police presence across the city during the world cup.
"We want everyone to have fun but our advice is, 'Please don't take your off-pitch celebrations too far and have a great cricket world cup experience'," he said.
Police also urged visitors and those going to games to take care on the roads.
Earlier today, tournament bosses said they were confident that the "sickness" of match-fixing wouldn't play a part in the tournament.
An anti-corruption unit inside the game's governing body, the International Cricket Council (ICC) has drawn up a list of people identified as being involved in match, or spot, fixing and illegal betting.
The names of dodgy gamblers and fixers have been passed on to law enforcement agencies to monitor and control, ICC chief executive, David Richardson said.
It was the best-prepared tournament he'd ever seen, with "no stone unturned" in regards to anti-corruption, security, and facilities.
The sport of cricket has been blighted by illegal betting and match fixing allegations and convictions in recent years.
The ICC says it now has "a far better idea" of those who travel the world trying to influence players, umpires and groundsmen.
For the past three years, its anti-corruption unit has been working with law enforcement agencies in both New Zealand and its tournament co-host Australia to gather intelligence.
They have also been working to "prevent and disrupt" any shady deals.
"We're in the best place ever to prevent any fixing," Mr Richardson said," he said at a pre-tournament press conference this morning in Christchurch which hosts the opening ceremony tomorrow, and the first game between New Zealand and Sri Lanka on Saturday .
While there could be no guarantee of a clean tournament, he said everything had been done to minimise the risk.
The global security threat was also "an issue", Mr Richardson said, but added there had been no direct threat to the tournament and was confident in security plans.
