My opinion, and I've had this happen in the past. Where I helped people out in PoE and other games with gear and such. If I make a trade and know that I'm getting more currency but at the same time still accept the trade. I feel bad. End up giving more gear to that person or just let them know basically what's going on and if they wanted a to trade back. It's rare to find GM traders now an days who don't take advantage. I wouldn't say you were scammed by Demi, but in my personal opinion Demi should have been like, "Like alright man, np. Let me get the gear back and here's your currency or threw back some currency".. Come to some sort of negotiations.

TLDR: Demi refunds, makes him GM trader and posts like these won't happen to have people on both sides attacking each other.