I'm sorry this is gnawing at you. And I can understand why, really we're not just talking about one scenario, but the combination of two.
What were you taught to do in zero vis?
I was taught that I was to get on the line and wait a few moments for the lead diver to make contact. After a few moments, if she had not come, go ahead and make my way to clearer water and wait.
I was also taught continuous touch contact if the diver made contact, but I know others are taught bump and go.
From the point where one made their way to clear water without the lead diver, it's essentially a lost diver drill. You calculate gas and wait.
Regardless, this is one of those scenarios that new buddies need to discuss before getting in the water. If you are the lead diver, and are expecting continuous contact because that is what you were taught, and your buddy was taught "bump and go," you may be in for a surprise when they leave.