I have similar issues with external USB Flash drives on Big Sur 11.0.1 (MacBook Pro (Retina, 15-inch, Mid 2015)). After plugging in USB drive I can't find it in Finder but it still can be founded under /Volumes folder. Open Finder -> Go -> Go to folder /Volumes (shortcut SHIFT + CMD + G). I hope it'll help.
javanlion
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
From
Kyiv, Ukraine
Post
Replies
Boosts
Views
Activity
Got the same problem on iPhone 11 Pro iOS 14.6 and CS-17 described solution helped! Thanks CS-17