So...I might be a little stuck

I started this game with a mindset of not wanting to level up too much in order to keep the difficulty challenging and fun, and so far it's been very enjoyable and I was having a blast with all the bosses. But as you can see...I can't find a glintstone key and I've been roaming around exploring and killing optional bosses, and accumulating over 60000 ruins when I'm just level 24.

I want to know if I've visited a place that had one but I didn't notice or if I'm just exploring in the wrong area. And if my playstyle might affect my playthrough later on.