by Joost Jansen on Boons which contains the full story in great detail. The article confirms what Nick F said above that the games would not be rated and also a recommendation that tournament organisers should get the scanners used to catch Boons. The following is a translation of the relevant paragraphs from the Dutch version:
"In Dieren he participated in the reserve group C. All the arbitrators there were now informed, and alerted to his strange behavior. During the first two rounds, nothing seemed to be wrong; the opposition was perhaps so weak that he needed little or no external help. This changed in the third round. His visit to the toilet increased to about 15 times per game, alternating with the three available toilet blocks. He often stayed there for 5-12 minutes, sometimes standing, mostly sitting (the toilet doors allow the feet to be visible). And I don't want to know from anyone how he or she sits on the toilet, but with one leg crossed over the other, so that there is only one foot on the floor ...? I have a picture of it.
Halfway through the fourth round, chief arbitrator Koos Stolk agreed. He waited for the player after the umpteenth visit to the toilet, and confronted him with our suspicions. He denied all allegations, and he even expressed indignation that he was suspected at all. By the way, he refused to be searched. That is indeed at odds with the Civil Code, but the FIDE Anti Cheating Guidelines do allow it. For the time being, Koos decided not to push the ball forward and let the player continue his match.
You would expect that after such a confrontation he would realise that he was being watched, but that was not apparent. He continued to frequent the toilets, sometimes after every move. From our arbitrator table, our intern Jarno Witkamp and I were able to observe him well, and we kept a kind of logbook for each game: which toilet does he visit, and for how long, and at what move. We also now had a nice collection of his games from Haarlem, Amsterdam and Dieren, which were subjected to a detailed analysis in the arbitrators' room.
I was by no means comfortable with it, if only because I was both at the NOVA tournament and at the Science Park arbitrator. Moreover, I witnessed the remarkable manoeuvres of the relevant player on a daily basis. I then enquired with Sernin van de Krol, fellow arbitrator and technician, whether an affordable scanner was available that could be used to locate a telephone without physical contact. Within a few minutes he had found one, which I immediately ordered.
Due to a misunderstanding with post.nl, the scanner was not delivered until the eighth round. We then immediately tried the thing out. The phone in the sock of Koos and even a metallic pen from Jarno were easily found with a bzzz, as well as the key ring and the phone in my own pocket.
After those successful tests, Koos has been waiting for the player. Together with Ron Bleeker, the arbitrator of his group, he informed him that he would like to examine him with a scanner. After endless sputtering and struggling, he seemed to agree. Koos called me in. But after a small demonstration: BZZ telephone, BZZ key ring, he would rather not be scanned. Koos told him that a refusal would be considered a positive scan result, and pointed out the consequences of this: removal from the tournament and reporting to the KNSB and FIDE, with the very conceivable result of a few years of suspension, plus the indelible label of cheater for the rest of his chess career. He finally admitted that he had a telephone with him, and Koos got him to hand it over. It was in an inner pocket of his pants. On the phone there were various chess apps, among other things, and a file with all his matches from the aforementioned tournaments. After a total of forty minutes, Koos carried out the investigation with great patience, the player left. His matches in the ONK have all been declared won for his opponents. They will not be processed for rating, and in anticipation of a decision by the disciplinary committee of the KNSB, his games from his previous tournaments have also been cancelled for rating processing.
Rarely have I been so content with the purchase of a device that I hope to use as little as possible. Incidentally, it can be borrowed for every arbitrator, if there is reason to do so."