logic would surely dictate

Such strange choices people make. The opening of the bin is obvious, and to claim that it was not noticed or was not obvious would be to either be extremely stupid, untruthful and possibly both. There is nothing impeding the bin-opening. Despite the bin's placement against two perpendicular walls (obscuring two of the four openings) two of the four openings are still visible and accessible. Placing the empty can carefully on the convex surface of the fag-stubbing-out-bit on top of the bin must surely have required more time and care than would have been necessary to get the can into one of the two large openings, where even a large degree of inaccuracy of aim would still result in successful deposition, even without the fine control required for the chosen method of placement.

It is more logical (and far easier (and more polite (and overall generally less bone-headed))) to place an empty can in the bin rather than on top of the bin (whence it might easily be displaced by wind or rain) but someone has chosen not to, presumably because they think or believe that it looks prettier on top like that.

Alternatively, someone placing something on top of the bin might claim to have been instructed to do so by the illustration on the side, which might be claimed to indicate the item of litter being dropped above the bin. Unfortunately this claim would not excuse and would merely illustrate an inability to consider how written instruction (particularly a fairly outdated and specific example, possibly second- or third-hand) might apply to the real world.



Unless the depositor felt guilty about sticking a recyclable item in a normal bin and had left it on top in case anyone passed by who knew the way to the nearest aluminum recycling bin, perhaps reasoning that there is almost certainly bound to be one inside the university building outside which the bin sits and that leaving the empty can on this particular bin would give it a good chance of being transported to the correct receptacle.