Welcome to the Community, gustavo. Let me share some information about why your vendor isn't showing in the Transaction detail report.
To determine if a vendor needs to be tracked for 1099 in QuickBooks Online, you should check if the vendor paid an amount above the annual threshold of $600. Also, credit card payments are not included in the reports, as the financial institution will report them.
Furthermore, you'll need to check if you're paying them from the correct expense account. When creating one, QuickBooks will use the expense accounts you've mapped to report 1099. If the amounts are inaccurately entered, it will sometimes cause this issue. That's why reviewing the payment transactions and accounts linked with them is advisable.
For reference, you can check this article: Troubleshoot missing contractors or wrong amounts on 1099s.
In addition, you can check this article to learn what to prepare for this year's payroll: Year-end checklist for QuickBooks Online Payroll.
If you have further question regarding why your vendor isn't showing on your report, you can always get back to us by replying to this post. The Community space is always here to assist you.