Sir Ian Wood, the matchmaker behind their ardent splashing and thrashing, had claimed the Scottish Government's estimates for North Sea oil reserves were up to 60% too high.
The Labour leader went off like a new well. Sir Ian was "the pre-eminent expert on North Sea oil", she gushed.
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He had "reluctantly entered the referendum debate as a father and a grandfather" to warn there were only 16.5billion barrels out there.
Did the First Minister agree with every word said by the nation's hydrocarbon hero? Did he get Wood or not?
Mr Salmond gave a glancing nod to Sir Ian's authority, then swiftly substituted his own expert, Prof Alex Kemp of Aberdeen University, one of his former economic advisers. Going by Prof Kemp's lights, the government's 24bn barrel estimate was a "robust figure".
But Sir Ian's was "a critique that we must address", insisted Ms Lamont. He says young voters need to remember the oil will be nigh gone when they're middle-aged.
And we all know how young people like to plan sensibly for middle-age. So can the FM tell our children and grandchildren why Sir Ian is wrong?
But the First Roughneck had come prepared. "My headline message for the youth of today - get involved. The North Sea oil industry will see you through your lifetime," he read.
The words of Ian Wood, 9 November 2012 on the BBC, he then explained.
Not only that, but, by happy coincidence, Prof Kemp had blogged that very morning to declare the 24bn estimate was indeed "plausible".
Labour MSPs were unimpressed with that.
"Listen, that's a lot of billions of barrels and Scotland should welcome it," said the FM.
Eyebrows upped in owlish surprise, Ms Lamont drawled: "Well, that'll give a lot of confidence to people worrying about the future."
The FM was simply saying "whatever has to be said to get by the moment" and ignoring the substance of the argument, she said.
Mr Salmond launched a supertanker of sarcasm. "This poor benighted country," he whimpered. "This poor benighted country, visited with a great curse of 15bn barrels of oil."
The SNP backbenches whooped it up and even Nicola Sturgeon, who has been restrained of late, flapped her arms in an exaggerated clap, like a sea lion in a baggy jumper.
All that oil sent Ms Lamont into a skid. "The First Minister calls Scotland a 'poor, benighted country'. It is not. It is a wonderful, wonderful country," she burbled.
She tried to recover by listing the FM's greatest referendum cock-ups, but to no avail
"Order," intervened Presiding Officer Tricia Marwick. "Ms Lamont, this is yer last question. Will ye just get tae it?"
Ms Lamont suggested Scots didn't trust Ms Salmond because he was a "man without a plan".
The FM replied that "perhaps the reality is that the Labour Party in Scotland does not have a Plan A, never mind a Plan B."
Ruth Davidson elicited a proper wobble by asking the FM the deceptively simple question: "Why does he think Sir Ian now feels so compelled to speak out?"
With a hard stare and a scowl, the FM stared at the floor for inspiration. "Sir Ian Wood wanted to clarify that his opinion was that the, eh..."
Och, could Ms Davidson not realise that whether it was 16.4, 24, 27 or umpteen billion it was still worth "trillions" in wholesale terms.
"Every country in the world would believe that that is an enormous asset. Why do only the Tories and the Labour Party believe that it is an extraordinary liability?"
Ms Davidson claimed that throughout the independence debate "the First Minister has twisted facts, ducked hard truths and simply closed his ears to anything that does not fit his lifelong obsession with independence".
Would he not concede Sir Ian was right to warn young voters about the medium-term outlook?
"For goodness' sake, don't misquote, this is an important argument," huffed the FM, sending ironic laughter ringing round the chamber.
He then reminded Ms Davidson of 40 years of Westminster perfidy and under-counting on oil.
Given that track record, did she not thing the UK government was up to its old tricks?
"Given the evidence, I think that most people in Scotland will say, 'Let's get our turn of using our main natural resources for the benefit of the Scottish people'," he concluded.
It all ended with a shuddering nosedive into raw campaigning.
After SNP backbencher Jim Eadie put in a cross about cancer mortality rates, the FM flicked the ball on to September 18.
"Jim Eadie mentions the importance of a public health service," he said. "I hope everyone in this chamber understands the importance of protecting and preserving our National Health Service in Scotland.
"It is absolutely vital. We believe that can be done through Scottish independence."
Don't rush to take a shower just yet though. There are still four weeks of this stuff left. Like the North Sea, it'll only get dirtier.