Sure sure, I don’t think anyone can prove that you pressed any button, without some logs or lots of effort. Even then someone else could’ve pressed that button as a joke or many millions of reasons or ways.
One can only speculate what is likely or unlikely to have happened.
It could well be a bug, or it could well be a mixup of settings, and you wouldn’t be the first to find OGS confusing or unintuitive, in particular the play page and all its settings.
See for example
and various discussions about improving the play page, in particular for new users and beginners alike.
Anyway regardless of what’s a bug or not you might find this helpful, it has some images and gifs
in particular this cog wheel brings up a menu to control automatch settings
while the custom game create button should bring up the window you tend to use (albeit in Dutch?)
and the create challenge or “uitdaging maken” creates the challenge with the settings and name you specified.
The correspondence button (Correspondentie) will use its own separate settings as mentioned above, probably by default looking for games with users of ±3 ranks and 2d would probably fall in that window.
That’s all I’ll say.