Could have just been lost in the mail maybe.
I would bet I have ordered from them over 20 times in the last year. This was the only time I have not received it. normally 7-9 days here as well. At this point either I will get a letter or one day it will show up. As you know the package and stealth is very small.
Sounds like someone swiped it. Or it got lost... You would have gotten the letter if customs got it. Good they refunded your money!
They dont use tracking anymore as it suffers more scrutiny via usps that way. They just send standard airmail now. My last order in october got here in like 5 days flat.