Just tested, its not there in English version too
I have no idea why - but today I launched portal and the cube is there o_O
Might be that you hadn’t got the latest update until you closed the game and it checked in. Closing, if you see the issue again, please report here - https://github.com/ValveSoftware/Source-1-Games/issues
Nothing extracted yet.
Makes it unpassable, its just not there ... also ... in previous chambers there were numerous situations of objects (cubes/droids/etc) falling through the floor.
I'm playing with russian localisation if that makes any difference