So here is how it went.
First I tried
gam print admins role "vault user" todrive
and it started but failed with an error
So I noticed I could search by roleID
I ran
gam print roles todrive
to get a list of admin roles defined in our domain
Then I ran
gam print admin role id:4917851638988823 (which is the Vault User admin roleID in our domain) todrive
That worked. It had a column for scope type which was either ORG_UNIT when then showed the OU that rights were assigned for, or CUSTOMER and nothing in the OU column which indicated that the person had the role assigned to the Vault data in the entire domain.
I could easily sort by OU and then by "assignedToUser" which is the email address of the account with the assignment.
That gave me the data I needed and actually I learned a couple things from this exercise.
Thank you Ross as always for your help.