With multiple jobs to tackle today my LR Catalog is MIA.
A quick .LRCAT search of my C drive only returned a blank cat dated today.
What is the name / location of the back up LR catalog I've been saving?
Have your operating system search ALL hard disks for .LRCAT files.
Backup catalogs are also named ending with .LRCAT if you have LR 5 or earlier, and the file name ends with LRCAT.ZIP if you have LR 6.
Suggestion: since you can change the location where backups are stored, then YOU need to know where the backups are being stored (not us here in the forum, because honestly we don't know where you are storing your backups).
When you close lightroom and it prompts for backup look at the backup location in that window. Hope that helps