The process for finding a thumb drive on a Mac is different from most other operating systems. Here’s how you can find it in any case.
The first step to do your search is by opening the “Finder” (the window) and clicking on “Go.” From there, click into each folder until you locate the file that has been lost. A further technique would be to use Spotlight Search which will also let you know when it locates files within folders or even if they are located more deeply down in the system than usual..

Why is my USB not showing up?

Your USB may not be showing up because of a few reasons. The most common reason is that its not plugged in all the way. Make sure to plug your USB into your computer and then try again. If you still cannot see your device, make sure that the port on your computer is working properly by trying another cable or port.

How do I fix my USB device not recognized Mac?

The most common reason for a USB device not being recognized is that the drivers are not installed. If you have recently updated your Mac, it is possible that your old drivers were removed and replaced with new ones. You can check to see if this is the case by opening up System Preferences, clicking on Hardware, then click on System Information. There will be a section called Drivers which will list all of the drivers currently installed in your system.