The 'pea' is 'hiding' in the lantern (or whatever). It's 'fine' size (+16 size), immobile and nearly invisible in its environment (+20 circumstance*). Assume that the base DC is 10 and you get a total DC of (10 + 20 + 16) 46.
* See Special: If you are invisible . . . under the description of the Hide skill. I'm assuming that the 'pea' appears as a glowing ember and would blend in quite nicely with the existing flame.