Cane went for an HIA at halftime in Yokohama, and passed it, but he did not return to the field with his teammates for the second half.
Match officials determined Cane had spent too much time off the field and so could not return, despite passing the concussion test.
According to World Rugby regulations, if a player is unable to return from an HIA after 10 minutes, or directly following the 15 minute halftime break, then he must be replaced.