Hey Ebaygum,
If I am to understand you correctly, you reset some aspect of your iPhone after not being able to receive mail from an account, and after that, you're not able to remove it again as it doesn't appear there. I'd be glad to see how I can help.
Since all of this started, have you had a chance to Restart your iPhone? If not, try that and see if you're able to use your iPhone as expected. Also, what type of email address is this? For example, a Yahoo!, Gmail, or Outlook account.
When you go to Settings > Passwords & Accounts, do you have the option to add the account back? If so, are you able to add the account with the correct credentials and check to see if it appears in Mail? If you haven't tried that, and restarting didn't help, do that now, and let me know what you find out.
Have a great day.