Finally got to make a proper description, as well as in studio photos and a herbarium collection of a Suillellus species I found last year for the first time. Posted it on Facebook at the time, where Machiel Noordeloos, Geoffrey Kibby, Davide Puddu and Michael Loizides mentioned the collection might be Suillellus mendax, rather than Suillellus luridus, based on the incomplete and concolourous reticulation on the stipe and the very velutinose pileus when young. Here are the links to the posts in "Paddestoelen Groep Nederland" and "British Mycological Society":