I'm over level 10..

Hidden quests might not be reflected in real-time, so if it's still not there after 1-2 hours, please contact supportㅜ Honestly, it'd be nice if they gave it to us before we asked, but what can you doㅜ We're the ones who want it, soㅜ

It's been almost two days.

Contact customer support directly. That's the fastest way.

Try reaching level 11, and if you still don't get the reward, don't go after the staff with a knife, just send in a support ticket haha

I usually wait about a day and then post an inquiry to customer support ^^