Hi gknair,
It depends a bit to the situation you are in.
When you are asking about our cloud solution where AIMMS hosts and manages the servers, we are able to help you out and we do have a log of all permissions/security related events. We can also restore your entire cloud-account to any moment in time; for an individual app this is not possible, although based on the security events it should be possible to reconstruct the prior settings and manually re-apply them. So if your question is about the cloud environment, please contact our user support.
If you are talking about a self-hosted on-premise PRO platform then there should be a logfile Security.log (and probably some with older timestamps) that contain those permission/security related events. If this is not the case, the PRO system administrator can update the log configuration file with the attached AimmsPROServerLog.xml. Security event logging was introduced with PRO 2.24, see https://documentation.aimms.com/pro-release-notes.html#aimms-pro-2-24-0-release, so the PRO server has to be sufficiently up to date as well. Also the PRO system administrator should be able to restore a snapshot of the database, again only the full database, not just a single app.