Thanks for providing in-depth details of your concern, Billavoider.
You have the option to include the depreciation account on the record if the value of the sold vehicle was depreciated. However, the remaining balance of the Long term Liability is still payable.
To remove the loan amount in the Balance Sheet report, you can create a journal entry. In this case, it would be best to consult your accountant. This way, you'll be guided accurately in choosing the category type of account to use in recording the transactions.
Just check out this article on how to record a journal entry: Create a journal entry in QuickBooks Desktop.
Just in case you need to track loans int he future, see Manually track loans in QuickBooks Desktop article for more details.
I've got a link here that provides you with articles about managing your reports: https://quickbooks.intuit.com/learn-support/en-us/reports/07?product=QuickBooks%20Desktop.
Keep me posted if you need a hand with reconciling your accounts or any QuickBooks related. I'll be here to help. Have a great day ahead.