"I was thinking a zero based 1120S and a Schedule C for the business dedutions and income"

First, that's just operations.

Second, if they paid themselves a wage, it is a deduction. So, they are missing that benefit, with your idea.

Third, if they took any money at all, and you both consider that Distribution, Dividend, or Draw, you are both wrong. You cannot take money from the corporation for personal funds and show no payroll if the shareholder(s) worked for the corporation. That's why it's called Reasonable Wage = for services provided, you get paid the going rate for that work and those efforts and that time spent.

If all of the work was done under the aegis of this corporation, which has its own FEIN as well, including all the protections incorporation offers (benefit plans, insurance, legal protection, contracts, etc), it's time to catch up all the missed and overlooked things.

If the person did all of 2022 business under their own name and SSN, then the corporation was overlooked entirely.