Welcome to Community, userbob-raley.
You can find a record of the bill payment check in your Chart of accounts.
Here's how:
- In the left navigation bar, go to Transactions, then Chart of accounts.
- Find your account that has the check in it.
- Click its View register option.
- Locate your check.
- Review its REF NO..
- The Reference Number is your check number.

I've also included a detailed resource about managing bill payments which may come in handy moving forward: Enter & manage bills/bill payments
I'll be here to help if there's any additional questions. Have a wonderful Monday!