If Arwoo said it ain't happening, then it ain't and you spent 20k NX on a gamble, and lost. That's the consequence of gambling, you might actually lose.
30 minutes is more than enough time to get a rare drop like the Black Bean Mark, Dominator Pendant, etc. that are total pains in the rear to get to drop at all.
Choose your words more carefully before you realize that rollbacks are not always good things. Besides it only affected EXP, it's not like every monster way exploding items everywhere... get real guys.
Why should they? They'd mess up a lot of people for their boo boo. Besides, Reboot got jacked due to someone crying foul on reddit over BiS items. Why should we suffer for that? 4x EXP is a nice compensation for screwing us over.