As an update, I will never buy from Mercari again. Their policy is that once feedback is left and/or 3 days have passed since delivery, they are done, no refund no matter if you find out you bought a counterfeit or spend three days waiting for a response. Trying to contact them put me in a loop of click contact, go to a page asking you to select your question, select return, be taken to my fake bag, click, be taken to a page with the policy saying sorry not sorry. Contacted Paypal.
Paypal messaged Mercari who sent me a paypal message with their policy and telling me in the future and to address my current complaint, to use their help center, which is the big click loop mentioned above. It is clearly a canned message and ignores mine saying hey I know your policy BUT...so I restated and resent. Meanwhile Mercari sends me a private message through their system that is almost the same as the one through paypal except this one threatens me that if I ever invoke paypal again they are canceling my Mercari account. Like I would use it again after this.
So I gave up trying to see if I could break the loop and really contact them (they don’t even have a reply button on the pm they sent me) and sent the case to Paypal to judge. I referred them to this thread, explained why I want an exception to the policy, and that I tried twice to reach a person at Mercari and was unable. Now I am waiting to hear if they will side with me or Mercari.