Mega Mush Unlock Bug

[Romiks]

I finally completed all hard-mode completion marks for all non tainted characters, but when i go to my item list (page 6, column 18, row 1) the item does not appear in the game.
I got the steam acchievement but it seems i didnt unlock the item in the game...

what can I do?

[Nazemec]

The item list shows items you picked up during runs, not unlocked ones. Not seeing it there immediately isn't a bug.

To check if it is unlocked on your save, the secrets list is the only 100% reliable way (main menu - stats - secrets). Mega Mush is number 547.