Yeah it really amused me that he went through tons of steps, buying lots of new hardware, etc before simply unchecking the delete images box.
Also a good idea to copy to multiple locations when importing. When I do professional work and import into Lightroom from SD card I have it set to create two copies - import to my external SSD (the "working" copy) and also copies the files to my NAS (which is then backed up to the cloud).
Nowhere in that process do I ever delete anything.