I had a similar situation as a buyer. I had been searching for something on German eBay and forgot to change the settings back. I then a couple of days later bought something from a seller in thr US which I subsequently wanted to return. The seller told me to do as you advised this seller but I couldn't do it because it wasn't coming up as an option on the German eBay site. Neither I nor the seller could understand why this was happening until I realised it was because I had been signed into the German site when I made the purchase. Leaving aside the tone etc it might not be a scam.
How was the problem solved?