Summary
At the moment, sysadmins/admins cannot see a private plan unless they have been explicitly granted access. It would be desirable that admins have access to all plans.

Use case
This is to allow sysadmins/admins to see Private Plans for cleaning up purpose, for example when the said use has left the company.

Workaround:

You can use the following DB edits, noting these were written in PSQL update per your DB requirements
Using the Desired plan ID and username insert the 0 and 1 permissions into that plan with the following for the user

INSERT into "AO_D9132D_PERMISSIONS" VALUES ('<USER NEME HERE>',0,(SELECT max("ID")+1 from "AO_D9132D_PERMISSIONS"),0,<PLAN_ID_HERE>);
INSERT into "AO_D9132D_PERMISSIONS" VALUES ('<USER NEME HERE>',0,(SELECT max("ID")+1 from "AO_D9132D_PERMISSIONS"),1,<PLAN_ID_HERE>);