Alolan Pokemon are showing up now in Go. I got the first two evolutions of all three starters already.
I've contacted them. Hopefully that gets some positive results, but given my previous experiences with things like this, I'm not very optimistic.I had the same problem with the Shiny Zacian/Zamazenta codes a while back. I'm not sure if they're just massively underestimating demand for these, or if they're purposely shorting stores, so customers have to come in multiple times (and hopefully buy multiple other things while they're in).
I contacted Gamestop itself, told them I tried to get the codes in stores and that they already ran out, and asked nicely if they could send me a code via e-mail...and it worked! So, if you just want the code and not the card itself, I'd probably try that way, it's likely FAR less of a hassle.