The correct answer to this question is The Problem Record. Details of a Workaround always be documented in the Problem Record. A 'Problem' is defined as the cause of one or more incidents, and the Problem Record includes the history of a Problem from the time it is discovered, or detection, to the time when it is solved, or closure.
Therefore, the Problem Record has information about all the details of a problem, which can be useful in case it needs to be referred back to in the future for a similar solution. These details include date and time of detection, the problem owner, description of symptoms, users/business areas/services that are affected, and the problem priority, along with information about workarounds and other history.