I hate PzIVs

[raz_atoth]

I'm quite sure the difficulty level doesn't affect the spotting process itself, just the info. in the interface which is presented to the user. For example, this is what the manual has to say on the differences between Elite and Warrior:

Enemy infantry icons are always the plain “soldier” type, regardless of their armament or function.

So, as i see it, the chances of spotting something are the same, irregardless of the difficulty.

In this particular case, it seems more like bad luck for Weasel. From my experience in CMx2 AT guns are more easily spotted than in CMx1, especially the big ones. You could conceal a gun in CMx1 until the enemy was really close, not so much in CMx2.