Don’t worry I am telling you the solution to this!
Sometimes, users faced pen drive detected but not showing on the computer because pen drive is not installed properly which is considered as one of the most general failures happened on pen drive devices. So, users can first try to update the USB drivers and check if it can assist to detect your missing pen drive. Here we take Windows 10 as an example.
1. Attach the pen drive into Computer.
2. Go to run and write devmgmt.msc to go to device manager
3. In Device manager go to Universal serial bus controllers. It should list the storage devices that you have connected to your PC.
4. Right hit the pen drive and then click Uninstall.
5. Remove the pen drive and restart your system.
6. Try to reconnect the pen drive again to check if the issue is resolved.