When looking at the cheque log, it tracks Posts and Prints.  Are you sure it said it was posted?  If so, you should see the Journal entry number and date there also that you can use to track in the Journal Entries report to see the actual entry.  You will also see the employee name and when you look at that employee in the Employee Detail report you should see the cheque (make sure the date range is correct based on the cheque log information).

However, if it only says you printed (which is my assumption), then it will take up a cheque number.  If you only printed to blank paper and the cheque number that was used still exists, you can reset the cheque number the next time you print or change it in the Setup, Reports & Forms, Cheques, pick the bank account, and change the Next Cheque No field in whichever section (Payables or Payroll, or the only one at the bottom) is applicable.

Thank you Richard, I didn't realize that it takes up the chq number if you print it and that's exactly what I did.

It's part of the audit trail in the program.  You be surprised how easily it can be to print a cheque, don't post, forge a signature, cash it and leave the country before it comes back at the end of the month on the statement.  The cheque log report was put into the system to help trap those types of things.  To be clear, I am not recommending anyone do this.

Hi Alana, when this happens to me it is either an online payment that you may have posted and didn't change it from cheque to some other way of payment, or a revenue canada payment in payroll that was paid through the bank and not by a cheque.