When is being stared at a sign of romantic interest? did I reciprocate wrong?

x-post from r/socialskillsYesterday the guy who puts sandwiches together at Panera stared into my eyes twice without blinking and I thought he was cute, so I looked right back and smiled.But now I'm thinking, why was he really staring? Was he romantically interested in me or fascinated by me, in a kind of horrified way? Why did he just stare without changing his expression? I guess that means he wasn't into me. Unless he's awkward as fuck like me. Ha. Or maybe he was high. High people confuse me so much.I need to learn how to flirt. Did I respond wrong? Should I have said something to feel him out? But what?