Level 2, 2 keys door (yes, again)

[bugout bob]

I have found the key beyond the teleport corridor

In the opposite corridor/room, I have found 2 buttons that open/close the other's wall. Is there a third button? If so, where... I swear I have scoured the corridor/rooms. If not, where is the second key?

[Myeka]

SpoilerShow

Well, as far as I remember, there's 3buttons, 1 for each secret room.