Just to clarify the issue:

It seems the ADAGIOSTYLES.INI file was corrupted. Custom style names were removed from the [Styles] numerical list and the attributes for those styles were placed before the [Styles] section, at the top of the file.

Manually restoring the file to its proper structure seems to have brought back the 'missing' styles but not sure how this occurred in the first place. The DIC only reported a discrepancy on a PO Header total.