I've never heard of it, but I wouldn't be surprised if we did.
But: It's not clear to me that the rule is at all relevant to that scam. As you describe it, it's not that the victims reasonably appeared to be agreeing to do one thing when what they signed said something different. They were persuaded to buy a blanket for x thousand dollars, and did.
The most obvious tool contract law has to undermine that is misrepresentation. If the scammer told a lie to get the victim to sign, then the contract's voidable by the victim. (This is true even if the misrep is innocent. If it's fraudulent, then you get a better measure of damages - and, of course, the scammers might've committed the criminal offence of fraud).
There's also a doctrine of 'undue influence', which if proved can also make the contract voidable.
Finally, even if the contract is valid, since R v Hinks [2000] UKHL 53, it's not impossible that the scammers could be convicted of theft of the money. So, validly transferred per civil law, theft per criminal law! Which is... surprising. (IMHO it's bloody stupid, but that's another debate).
But: It's not clear to me that the rule is at all relevant to that scam. As you describe it, it's not that the victims reasonably appeared to be agreeing to do one thing when what they signed said something different. They were persuaded to buy a blanket for x thousand dollars, and did.
The most obvious tool contract law has to undermine that is misrepresentation. If the scammer told a lie to get the victim to sign, then the contract's voidable by the victim. (This is true even if the misrep is innocent. If it's fraudulent, then you get a better measure of damages - and, of course, the scammers might've committed the criminal offence of fraud).
There's also a doctrine of 'undue influence', which if proved can also make the contract voidable.
Finally, even if the contract is valid, since R v Hinks [2000] UKHL 53, it's not impossible that the scammers could be convicted of theft of the money. So, validly transferred per civil law, theft per criminal law! Which is... surprising. (IMHO it's bloody stupid, but that's another debate).