Hmm... so the numbered things we have (and haven't used in some way) are:
--The "12/6" on the baseball diamond
--The number 4 on the hopscotch, which is now blue
Putting these together to make 4126 or 1264 would be 4 digits, which is too many. Adding 4+12+6 gives 22, which is only two digits. Multiplying them, however, gives 288, which is the right number of digits. The good thing about this is that it doesn't require a specific order for the numbers, in other words it doesn't matter if the 4 is "before" or "after" the 12 and the 6.
On the other hand, this makes the poem and the fact that it's on a baseball diamond seem entirely superfluous. Those are the other two things that I don't believe we have made any use of. Does anyone have a better idea?
Oh, I just realized that maybe the 12/6 is meant to signify division, which would give 2. But then we would need a third digit (in addition to 2 and 4), and also a way of ordering the three, which seems quite difficult. We could maybe conclude that the 4 should be last, since we found that out last, and this should have been true for any path of solving the puzzles (since we needed to line up all the dials to get the hook to open the traffic light). However, everything else depended on which places we looked into in what order.
We do have a third digit: the 7 on the bottom panel of the trafic light.
The three digits should be 2, 4 and 7.....but I don't know how to order them.
I somehow missed that about the 7! Anyway, that pretty much eliminates the idea that they need to be ordered by when they appeared. By the "underside of the panel that hinged open" I assume that actually meant the original top side, the one that was facing into the compartment, otherwise you would have noticed it when first examining the light. So the 4 and the 7 were revealed by the same exact occurrence, the opening of the compartment.
I'm thinking maybe they should be in the order 247, though. There have been quite a few references to years, dates, and other measurements of time in this puzzle, and that could refer to "24/7", which also involves time.
I hadn't even thought of the 12/6 as signifying division - impressive logic! And yes, you're correct about the location of the 7.
Now that we have the three digits (2, 4, 7), the obvious next step is to figure out their order. And the only things we haven't used are that ski jacket from the closet and the poem on the back of the charcoal drawing, so I'd guess the clue is somewhere in there?