I’d check with the operators of the store (SammyG and Captain_Nemo) so that they can track down whether this is a problem on their end or on (say) your bank’s end.
“Last Friday” is around the time that they were having problems with the shop point system, causing them to turn off the point system in the shop (Reward coupon is not working on TheSapienShop ). I don’t know the exact timing of all of that. But perhaps your transaction got caught in the middle of all that and in the middle of their efforts to set right transactions affected by the shop point system.
Contact (via DM as well as through the shop’s Contact form, with a clear Subject line) Sammy and Cap’n.
And understand that Sammy may still be celebrating his recent wedding, so he may be slow in getting back to you.