If you have deleted your Google Merchant Center account, you have the option to recover your account within 30 days.
If you were the admin of the account, you can fill out this form: https://support.google.com/merchants/contact/howto2
What If It Was Longer Than 30 Days?
In that case, you can fill out the form above, but most likely, it will be lost forever, and you will have to start from scratch. This means you have to create a new account.
When you do create a new account, do so from the place of operation (where you work, where your business is located, do not spoof, use VPNs, etc)
If you lost your account because someone removed you, you should never give admin access if you have people working on your account. There is no need for this.
I only ask for admin access for my permanent clients, whom I manage full-time, and I only ask for standard access for clients I do small jobs. A standard user can do everything except add other users, add new features, etc. I ask my client to enable extra features when needed in these cases. You have some additional tasks, but you are safeguarding your account. Of course, giving admin access is absolutely fine for people you know.