I don't know what seller you bought from, but a lot of the Olaplex sellers I see on the main default pages for Olaplex products are "Fulfilled by Amazon," like this: http://www.amazon.com/Olaplex-Traveling-Stylist-Hair-Types/dp/B00SXVVM28/ref=pd_sim_194_2?ie=UTF8&dpID=41u97GGw5RL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=03B7GET6WVPJGKASXYN7

Fulfilled by Amazon means the product is shipped from an Amazon warehouse.

But even if your order was shipped directly from the seller, it could be counterfeit. If they can make counterfeit MAC and Urban Decay makeup, which is widely available to everyone, they can make counterfeit Olaplex.

The product reviews on Amazon are pooled among all the different sellers too, so I don't see how you could differentiate which seller each review is for. The reseller ratings on the seller page just say "Great product" and "Fast shipping" don't specify what product the user bought, so I don't see how consumers are supposed to tell based on the reviews whether the product they're getting is authentic.