Do you scoop once per day or twice?

The recommendation is, one box per cat, if you scoop once per day. (Up to 3 cats. After 3 cats, you n eed a box per cat plus one extra box..) So if you have 2 cats and go down to one box, you need to scoop morning and evening.

And as you already discovered, don't leave anything around to remind them of the missing box!

I'm just not sure if they can do this. I have never removed a box.