HOW DO WE, AS BI WOMEN, HIT ON LADIES IN "STRAIGHT" BARS???

In an effort to recover from my horrible date last night, I went out with one of my favorite human beings one earth. While dancing, a ladyperson with crazy curly hair (seriously, that is my kryptonite) and a generally awesome air about her started shouting at the band to play Everlasting Light, one of my favorite songs. I realized then and there that I had NO idea how to hit on a woman in a "straight" bar. With women, I've always either been hit on first, or I've known their status beforehand. I apparently have no "gaydar" (and yes, I know that that's not really a thing, but it still makes me feel bad). I started talking to her, I danced with her (not uncommon for girls to do together at bars, even straight ones), I made her laugh. I went to the bathroom, started panic texting a certain GTer about what I should do, and decided (while texting with really just myself) that buying her a beer was the way to go. When I came out, the lovely curly haired lady was gone. My (straight) friend who I was there with said she probably didn't realize I was interested, and didn't think anything of walking away from a girl without saying anything. I of course was freaking out that I was coming off as a creeper.

Seriously, queer women of Groupthink, how do you approach a woman who you have no idea if she is into the ladies?