I really do suffer of "us versus them" mentality, but it has nothing to do with Americans or any other nation, for me it is "people who know what they are talking about vs people who don't". Needless to say, there will always be time for you to grow out of this second group.
And the link is relevant. You just don't understand it, cause you lack knowledge on obligation law. Ratio is as follows: trade or sale are consensual contracts. that means that there needs to be consensus between parties regarding the most important parts of contract such as item properties, price etc. If parties do not agree on all of these elements, there is no contract, it becomes void, ergo there is 'absence of basis', and you misunderstood the example given. The contract in that example became void, not incomplete or unfinished. In those cases this institute is applied, and it creates 'an obligation to make restitution arises, regardless of liability for wrongdoing'.
The reason why I didn't mention specific country is obvious, this institute is part of legal system of all continental countries, and being a remnant of Roman law, it is also incorporated in statutory law of common law countries. The fact that you don't know about it doesn't make it irrelevant.
Get it?
Btw, U mad bro?