Why my app disappear at reboot?
I finally found out why! :D

When the phone boots - at least if I use go launcher - if the sd card is not completely mounted apps "get lost".
I've completely solved the problem activating my phone card pin code.
I turn on the phone, wait on the pin code screen without entering it for a minute and then I enter the pin: everything is perfect.
I think the problem can be also solved killing and restarting the launcher but I didn't test.