You can try using a data recovery app to see if you can recover anything from the 32GB USB stick, but it is highly unlikely you will recover anything from the internal SSD due to how SSDs work. Once an item is deleted from an SSD and the Trash is emptied, then there is no way to recover the item. Since the items disappeared during a macOS transfer, the missing items would not have been placed in the Trash (or highly unlikely).
When transferring files to another drive, it is best to perform a copy so that the original items are left untouched. If you "move" items to an external drive, then both the original items and the items already transferred to the destination seem to all get lost if anything interrupts the "move" operation. Usually transferring items to another drive results in a "copy" operation by default which should in theory leave the original items untouched. Usually a user must manually trigger a "move" operation when transferring items to another drive.
You should always have frequent and regular backups of your computer and all external media (including the cloud) which contains important & unique data.
Edit: I have used the data recovery app Data Rescue in the past:
https://www.prosofteng.com/