Unless of course they weren't even thinking of it in a context of Trayvon possibly stashing something (lots of evidence of this sort of lack of pursuing Trayvon-negative scenarios) or by the time the FDLE was brought in (which took a long while) any such evidence was gone.
Weeks go by and a little black and mild blunt behind some bushes or in grass, which was rained on at least once... in some shadowed corner of a long walkway, is found by FDLE... under the best case scenario where they actually care to look, and they're going to be able to declare it connected to the case how? It won't have fingerprints at that point from Trayvon... etc, even a screwdriver is going to be really hard for them to connect to the case in any way.
But the better retort I can give you is that Trayvon had more than enough time to go drop anything incriminating at the porch of Brandy Green's apartment.
The amount of time he disappeared for combined with what Deedee said about him being right by his father's house, combined with him paying 3 doofuses at 7-11 to buy him blunts, combined with 2 occasions when Brandy or his father referred to him being out on the porch before he was killed, all add up to a pretty convincing reason to think he dropped something off on that porch before going back northward to assault GZ.
Was it a blunt? a screwdriver? both? Additional items? Other stuff entirely? Robitussin obtained from Walmart during the extremely long gap of time between him leaving 7-11 and getting back to the gated community?
Who knows? These aren't unreasonable speculations given the 7-11 footage and his facebook posts, and what people said about him being on the porch though.
I personally doubt that he was intending to burglarize anyone during the same outing he went to 7-11 on.
However I think it is extremely likely that he burglarized homes in that community on previous occasions. Being caught with 12 pieces of real gold women's jewelry in his backpack at school, along with a bent screwdriver which the school security guard had no doubts as to the implications of... but which the Miami police could not match to any stolen jewelry reports, indicates to me that he was likely using Sanford as a burglary source, then selling the goods in Miami.
GZ did mention him looking at houses in a way that was suspicious.
Maybe Trayvon was taking his time getting home, and using it as an opportunity to see if he could spot any tempting looking houses to return to later that night, it was early yet after all and I don't think he'd want to be lugging around a big can of juice etc while climbing in a window.