The stores around me all ran out in a couple days. It's a two week event. Hopefully they print and distribute more or release it another way. When Legends Arceus came out they didn't have enough preorder bonuses at the store I preordered mine at, so they gave them to the customers who picked them up first, rather than those who preordered first.
I know I'm almost ten days late for this post, but to answer the question, yeah, it's not just you.
I finally went to get my codes today (I kind of forgot about it) and the store I went to had only received their codes either today or yesterday. The cashier still had like two stacks that he hadn't unwrapped from the plastic yet because (he said) all the marketing hype had kinda fallen away, since the event's been going on for a while now. This has happened before to either this store or another in my area (can't remember which) and it makes me wonder what the deal is.
Unfortunately, I wasn't able to get a code since my local GameStop ran out of codes a week ago. Hopefully they change their method for these kinds of giveaways in the future since it seems like they sent out a limited number of codes.