Guys, as you said it was all an illusion... There was absolutely nothing wrong with the blade. The hamon continued normally after the yokote as it should be expected. And on top of that, it did not even change shape. It stayed as a subtle elegant suguha. So it was a koto blade after all. A beautiful blade with tight hada, no kizu, and a magnificent o-kissaki (you know how hard they are to come across). It was all dressed in a fabulous koshirae, with an awesome saya of lacquered same.
But... But, somebody beat me to it..
This sword was in the shop for less than 3 weeks and 3 people were really interested in it. The lucky buyer hasn't even seen the blade yet! He bought it because of the saya. Apparently it will allow him to create a daisho with a katana he already has. You see, it is not your average same-wrapped saya. It is made entirely of the largest nodules. I started counting the 'king' nudules in the saya, and me and the dealer concluded that more than 70-80 rayfish died to create that one saya :D :D
Well, I believe that the lucky buyer will be happy when he finds out that there is a pretty decent blade under this koshirae.
I didn't leave empty-handed though. I purchased an echizen school hira-zukuri waki with a wild, almost hitatsura-like hamon, in a pretty decent koshirae.