Were a lot of inactive games just deleted?
It had been a year since the script to clean up inactive games was run, so yes, a lot of old games were affected.
There is no 'notice' given by the system before this happens - the script removes games that have had no posts for a long time. RPoL is not meant as a repository for games that aren't in active use.
If you wish to store games for notes, etc., please make a copy of what you wish to keep offsite, whether on your own local machine, cloud storage, etc.