I'm loving the depth of analysis that some will go to in order to be right, including noting holidays and number of emails. What I don't love is how mean it is.
Despite the fact that OP will almost certainly get his money back (OP, did you use a credit card with any protection?), it is very scary to be scammed. I don't understand the wish to pick apart the story before we see any reason at all to doubt it. If the actual reseller wants to jump in and offer their side of the story - now that seems fair - but that hasn't happened yet as Monicca is "unaffiliated with Reebonz".
FWIW I have had plenty of shipments from HK that arrived within a couple days. I've also had emails from my Hermès SAs and from after-sales care on Sundays and holidays.
What is worth paying attention to is that this was a clearly used and much carried Birkin that went through a reseller. It certainly appears questionable to say the least and if counterfeit it is likely that the previous owner may not have been aware of this. This is how fakes end up "in the system".
When buying at resale it behooves us all to pay the nominal sum for an expert authenticator, by which I mean bababebi (I am not aware of an equivalent) and to use a payment method that offers long term protection (Amex Platinum: 90 days, Chase Sapphire and Amex Centurion: 120 days or more).