The reason MMORPGs adopt a "one-time restore" policy is because it's a lot of work to fish out and restore selective data, and they have a lot of players. The more requests they entertain, the more overwhelmed they'll be with such requests, to the point of it being unsustainable. So they want you to think very carefully about if the thing you want to restore is the most precious thing to you or not - for example, it could be an Ultimate weapon and don't think you'll clear again, an expensive mog station item, a now-unobtainable item or an Eternal Bonding ring.

In most cases, items aren't important or can be obtained again. Usually easily, but even if not, it's usually not worth burning a restore on. It's unfortunate that you didn't realize that deleting meant deleting but, in fairness, you did click a delete button. It would have no meaning if it was not doing that.

In any case, this forum is meant for Localization issues (which means the translation of Japanese to English, grammar, spelling and other text issues). I would suggest posting it in General Discussion.