Sent from my SCH-I535 using Tapatalk 2
I've got same problem yesterday, after multiple automatic updates from the google play - app drawer icon and all custom icons disappeared from the dock. I replaced custom icons, but wasn't able to get app drawer icon back and could access the drawer.
there is no launcher settings in the menu, nor in the desktop options, and even in the launcher options in the system settings there is no option to bring back the app drawer icon. force-stopping launcher, restarting phone, cleaning cash and even dalvik cash doesn't help either.
the only way to bring it back that worked, was clearing all data for trebuchet :
Deleting app data is not a solution. It's a workaround.
After searching for a long time I consider this to be a big ups in the Trebuchet design.
I use 3 panels in the quick launch for apps (botton) and I can't create duplicated app drawer buttons for the alternative panels... Not nice.