Top official Sir Tom Scholar allegedly had to have his phone reset, which meant his replies to the former prime minister were deleted, the Mirror reported.
Cameron sent dozens of messages to senior officials and ministers, pleading in vain for government cash to prop up failed financiers Greensill Capital.
But Sir Tom Scholar, the permanent secretary at the Treasury was unable to publish his replies to 12 messages from Mr Cameron because his phone had been reset.
The error was revealed in response to a Freedom of Information request filed by Bloomberg.
In one of Cameron’s messages to Sir Tom on 6 March, the former PM seemed to predict a Bank of England interest rate cut five days before it was announced.
What Cameron said
Mr Cameron’s texts read: “Never quite understood how rate cuts help a pandemic.”
Officials are legally barred from disclosing market sensitive information about changes to interest rates.
But Mr Cameron insisted last week it had been an autocorrect error and he was referring to a VAT cut.
He told the committee: “I’ve been rather baffled by this text message because obviously rate cuts are a very appropriate thing to do at a time of difficulty.
“I think I’m a victim of spellcheck here – I think it was about a VAT cut… I think I was responding to something that was in the news.”
Sir Tom’s password blunder means his response to the former Prime Minister may never see the light of day.
Mr Cameron’s messages – some of which were signed off “Love DC” – were disclosed during an investigation into lobbying by the Commons Treasury Committee.
Messages “not available” to the public
But when Bloomberg filed a Freedom of Information request to the Treasury requesting to make the replies public, they were told the messages were not available.
A Treasury spokesperson said: “On 1 June last year, Mr Scholar’s mobile phone had to be reset, after being automatically locked when an incorrect password was entered several times.”
The Treasury said resetting the phone was a “standard security feature on Treasury mobile phones” – but did not say whether it was Sir Tom himself who had entered the wrong password.
Appearing before the Commons Public Accounts Committee last year, Sir Tom admitted Cameron was “persistent” – before passing him on to Treasury civil servant Charles Roxburgh.