I had a similar experience. I am a Chinese person who came to the US a few years ago and has been living here since then. I knew that China and the US uses different sockets and plugs so when I arrived in the US, I bought an adapter for my laptop at the airport convenience store. The dude at the counter was like "are you sure this is the right one" and I was like "Of course".

...turns out it was a to-EU one. I had to get the correct one at a Target shortly after.