upgrade to OS 11.5.2 lost Word docs

Just restore them from you TM backup. If you don't have a backup then please do the following and we can look for obvious issues:

Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again.

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211

Welcome to the Apple Support Communities.

Can you restore those files from Time Machine: Restore items backed up with Time Machine on Mac - Apple Support?

Cheers,

Jack

Did you possibly upgrade to macOS 11.5.2 from an older version of macOS (macOS 10.14 or earlier) and with an older version of Microsoft Office (2011 or earlier) installed, and lose your older Office apps, and not your documents? Because old versions of Office (2011 or earlier) won’t work on macOS 10.15, on macOS 11, or later.

If you lost some number of Office documents but not all of your Office documents, and if you are using Office 2016, Office 2019, or Office 365 subscriptions, then you will want to check your backups, as others have mentioned.