Same here - I can find 6, can't find the 7th. As for the room you're talking about with the slope, if that's the one with the ladder in the middle of the room, you get on top of that 2-tall block from the other side. In the room where you have to make a 3-step "staircase" just past the ladder, you fall down the right side to come in the "back" way.
If you didn't get that totem, and you still got 6, then you've clearly found the one I didn't, and I can't even guess where.