Great!
Yes, -99 is the culprit and its a BUG. I will have to check the JIRA later to see what could be a potential work around for this, if any, to stop this happening. The root cause for -99 is, when an operation is initiated from the UI and at the same time the system goes down or the performance is pegged badly, the transaction at the DB end is not completed or rolled back and this comes back with a -99 in the last_updated_by which results in the record missing from the UI.
The work around as you mentioned, is to update the column in DB to 1(admin) and later you can make some changes to that record from UI to show your 5million ID.
Please mark this discussion as answered which will help other community users facing a similar problem in future.
Thanks,
Jerin
CA Support