I’m using leap, and every now and then my network icon disappears. I’m using internet by cable, but the same issue happens if I’m connected through wi-fi. It’s also worth mentioning that I also do not have Dropbox icon (just like the network icon, the dropbox icon is non existent and there is only a gap or space on the notification panel where the icon should be)
I was seeing the network icon overlaid by the “hidden tray” icon. Clicking that have me the hidden tray icons. But clicking on the space to the left of the overlay gave me access to NetworkManager.
I have Intel graphics. I reconfigured to use uxa acceleration (instead of the sna default). And it now seems to be better. But I’ll wait for a few more reboot/login cycles before I’m sure of that.
I’ve reported this issue to bugzilla, when I find the thread ill post it ehre 
I’m currently using nvidia geforce 210 gpu with proprietary driver