If the USB stick physical drive is seen by macOS in the System Profiler or within Disk Utility, then you can try using a data recovery app such as Data Rescue or Stellar Data Recovery. Within Disk Utility you may need to click "View" and select "Show All Devices" before the physical drives appear on the left pane of Disk Utility.
If the physical drive is not seen, then you have a hardware issue of some sort (USB stick, or USB-C port, or adapter/dock/hub). Try disconnecting all other external devices from the Mac in case one of them is causing a problem.
FYI, don't store the only copy of any important data on a USB stick since USB sticks are very unreliable. Even popular name brand USB sticks are not that reliable.
Also, people should have frequent and regular backups of their computer and all external media (including the cloud) which contains important & unique data. People should never have just a single copy of any important data.