Posted and cut check for an AP Batch but the period for the GL was closed

We are closing 2012 and after reviewing the reports, have discovered that one of our AP bookkeepers entered, posted and cut the check for a batch in an open AP period but a closed GL period.  So the transaction is fine on the AP side but missing from the GL side.

Ideas on how we can correct this?  

We are still on GP 10.0.

Thanks in advance,

Pam Muzyka