This panel serves as the main panel and has H+H+G, the neutral is not connected to any lug and lays at the bottom of the panel. What (NEC) section allows or justifies this? Thanks
Is this the service panel or a sub-panel? Since they ran a 4 conductor cable I would guess that it’s a subpanel which means that you need to use all 4 conductors. If it’s actually a service then the answer is less clear.
Service panel
Perhaps they ran SER because they had it instead of SE. If so the ground, now neutral, is most likely too small.
If this is a main panel the answer is not 100% straight forward, but, in a nut shell the white should be on the neutral lug not the ground. However, it might technically be ok since the NEC does allow for a neutral to be bare at the service entrance and smaller then the phase conductors.