The cabinet was held his laptop which had not been taken. Amounts of cash on left by staff on desks around the office had not been taken either.
"It seemed a very odd thing at the time and I presume that someone may have been interested in the information that was on that laptop" Ms Collins said.
It's one of a series of interesting little break ins around computers, she told the Herald.
She said that included the break ins at Mr Mitchells' offices in September and October last year in which a laptop and phones were stolen.
Mr Mitchell also told the Herald on Sunday his email was hacked during those burglaries.
Ms Collins and Mr Mitchell's reports of break ins come as the Government responds to Nicky Hager's book Dirty Politics with claims the writer and the left in general are the ones indulging in dirty tricks such as the hacking of blogger Cameron Slater's website which yielded the messages Hager based his book on.