This issue can be caused either by file corruption or by a network disconnection issue.
1.  Process the Error log to determine if there was any corruption on files.
2.  If there are no file errors for the posted date in the errlog.ws report, then this issue was caused by a network disconnection.

Solution:
1.  Key in a manual journal entry for the missing obligation, or
2.  a.  The obligation can be voided out of AP
     b.  The voided batch can be reversed in GL
     c.  The obligation can be entered again using the correct business date.  
     d.  Verify a trace report was created in the Print Manager for the posted obligation.