There's a detailed article in the NYTimes discussing the first case in Seattle and the contact tracing that was done.
While it sounds likely that he was the index patient in Seattle, recently, they discovered a nearly-identical virus circulating in British Columbia. It is possible someone else who had traveled from Wuhan in the same timeframe was the root of the Washington (and subsequent national) spread, so it was not necessarily a failure in contact tracing.
"In recent days, the sequencing of new cases has revealed a surprising new possibility. A series of cases in British Columbia carried a genetic footprint very similar to the case of the Wuhan traveler. That opened up the possibility that someone could have carried that same branch of the virus from Wuhan to British Columbia or somewhere else in the region at nearly the same time. Perhaps it was that person whose illness had sparked the fateful outbreak."
https://www.nytimes.com/2020/04/22/us/co...ncing.html
While it sounds likely that he was the index patient in Seattle, recently, they discovered a nearly-identical virus circulating in British Columbia. It is possible someone else who had traveled from Wuhan in the same timeframe was the root of the Washington (and subsequent national) spread, so it was not necessarily a failure in contact tracing.
"In recent days, the sequencing of new cases has revealed a surprising new possibility. A series of cases in British Columbia carried a genetic footprint very similar to the case of the Wuhan traveler. That opened up the possibility that someone could have carried that same branch of the virus from Wuhan to British Columbia or somewhere else in the region at nearly the same time. Perhaps it was that person whose illness had sparked the fateful outbreak."
https://www.nytimes.com/2020/04/22/us/co...ncing.html