Errored workflows for terminated employees

We have few workflows, for example, iExpense transaction which has been submitted by an employee who is no longer part of the company. The APEXP workflow has errored out as the userID is not longer active. This employee has to be paid for the expenses submitted as part of the expense report. What is the best method/industry practice to process this errored workflow? Do we enable the userid for a brief time and process? This is causing audit issues for us and we would like to know if we have an alternative way to process the recurring business sceanrio.