It was detected in European samples (Spain, Italy) collected as early as March 2019 and is likely to have been spreading around the US by that point already.

https://www.reuters.com/article/us-health-coronavirus-spain-...

Those claims were never published in peer reviewed journals and were very likely just false positives:

https://en.ara.cat/society/inaccurate-data-led-to-belief-tha...