@HenrysAxe
Data loss extremely rare and usually proceeded by user intervention
Calibre settings are stored in the (usually hidden) <configuration folder>.
These include the location of the last used Library.
These are NEVER deleted by uninstalling.
That folder is why an update knows where to find the existing Library.
Are you running some sort of 'Cleaner'

software?
Are your user files kept on some sort of a Network/cloud server?
Bottom line: You need to have done OTHER things to break(lose) the Library. An update won't do that. Messing around inside the Library folder
can