ascended stuff
Infusing an item means giving it agony resistence WITHOUT any upgrades. It also requires doing fractals to get the necessary items. http://wiki.guildwars2.com/wiki/Infused_equipment
Additionally I would use that to make it account bound to equip on another character. Using both an infused and uninfused “unique” item seems like an unintended loophole that might get fixed.
It happened to other players as well and they were compensated with another ring.
Contact support and tell them what happened to you.
For more information about the other happenings:
https://forum-en.gw2archive.eu/forum/game/gw2/No-warning-about-ascended-rings/page/4#post1834804
https://forum-en.gw2archive.eu/forum/game/gw2/Can-not-use-the-same-Ascended-item-twice/first#post1889375