What a shame to hear! It realy sucks when that happens becuase now you are tinking twice before you trade again. I once had it also.
I was trading a card with some guy and like you i send it the next day as soon as i could. After a week i still had no card (we were in the same smal country). I kept e-mailing him where my card was and such. He gave me excuse after excuse. Til at one point i got fed up with it and made a police report( just for the sake of being scammed. Its a crime.) He also got an e-mail that i made a report.
He started e-mailing me like crazy saying he is sorry, the card is on its way with somthing extra. And i got the card two days after with a extra card!
When i started trading amiibo cards on here i was also a bit scared. But the comunity is great and every card arived so far. I made 12 trades already.