Hmm.. Ive been trying a few things here and there now and I realized that since my BB9000 has upgraded to OS 5.0.0.592, Any app I install, they dont show up in my downloads folder anymore... but they're in the application list.
I mean the applications list in the options, not the applications folder.
EDIT:
So I tried with other apps.. I saw that they would pop up under applications AND downloads.. randomly,
but NOT appworld.. appworld just doesnt show in any folder, only in the application list (in options), I did installing it again on top of it, nothing working
I've had that happen after upgrades before. Just reinstall it over the top of itself and the icon will come back.
Like apbthe3 says - just reinstall it over the top. This happens to me every time I upgrade. The App World icon always disappears. But reinstalling it over the top of itself will bring it back.