One of by banking accounts disappeared. How can I restore it?

It would be my pleasure to help you restore missing banking accounts, @marenmaggiemegha.

Making an account inactive could be the possible reason why one of your banking accounts disappeared. Let's verify by using the Audit trail to see if an account has been accidentally deleted. 

Here's how:

1. Go to the Settings icon. 
2. Under Tools, choose Audit Log.
3. Click the Filter button. 
4. Use the fields on the page to choose the appropriate User, Date, or Events filter.
5. Once done, select Apply to see the results.
   
   
   

Otherwise, you can click the Include inactive option to see all banking accounts including the deleted ones. When you see the missing account in the list, just click the Make Active button to restore it. Please see the screenshot below for your visual reference: 

Furthermore, I've attached a link to help you manage your bank accounts in QuickBooks. It contains information on how to edit, hide or add an account number. 

Count me in if you need further help handling banking transactions in QuickBooks. I'll be here to help. Take care and have a pleasant day!