I purchased a ring then it's gone.. after a while

Hi

Well, I started playing Path of Exile again. I was not into it at all.. I am still new to this game.

After few days play (first time for the awakening), for the first time, I did three tradings after watching Ziddgy's youtube video.

First trade was 'a Chest'.
Second trade was 'two handed weapon'
And the last one was 'a ring'.

Then something happened after purchasing the ring. I did not play the game after the last trade.. just browsing the forum and tradings.. trying to fill up my resistance.

Then all of sudden, the ring I was wearing disappeared!!!

What the??? I clicked through my inventory (got a lot of useless stuffs) and not there.

Wow!! It was already too late last night. so I went sleep and writing this in the morning. Someone in the chatting mentioned something about 'Roll-Back'.

I am curious what happened. Was it a trade scheme? I am a bit concerned about trading.

I am trying to finish Merciless for the first time and this is very encouraging..

Did you leave it in a crafting bench?

yes. silly. beginner's mistake.... embarrasing.....