AP Check Not Showing in the General Ledger

Most likely the GL transactions were created in a GL period other than what you are thinking.  To find where the GL transactions are sitting, call up the vendor to which the check was issued in Vendor Status.  Access the Checks tab and locate the check in question.  Right click on the check and choose "View Related GL Transactions."  You can review these transactions to see what period the GL transactions are in as well as what GL accounts were impacted by the writing of the check.