TL;DR: There may be a white knight in my social circle

Earlier this year I got a lay, let's call her R. Now the thing is she is a "friend" of a guy I'm pretty cool with, let's call him A. Despite the flakes and red flags (I'm still learning) we still managed to see each other every weekend. Our text interactions were pretty bad, and a few weeks she ended up texting me she wasn't feeling me. That same week she told me that we were at the same party and she came to me and it was like she never told me that.This would continue to happen for the next few weeks. Now, after a party on Saturday night she insists that we meet up the next day (there's a post about this). She ended up flaking so I nexted her.

The problem is I don't save numbers. A few days later I mistakenly sent a text to R thinking it was someone else. The text went something like "Hey, are you okay?" I didn't pay much attention to it because I thought I sent it to someone, but apparently she took it the wrong way. R went back to the guy who was pretty close to me, and said something about how I'm a bad person (typical) and God knowns what else they talked about to me. A pulls me aside as tells me that R has been talking to him about me, and that his advice to me was for me to delete her number and texts. I was confused at first, but after going through my texts I realized that I texted R. However, I did not notice she responded to my text and gave no indication that I was bothering her. I didn't tell R that the text was not meant for her, but I did tell A that the text I sent was to someone else and not R. While A insisted that he was not taking any sides, he gave off the impression that he was.

I've always had suspicions that A had a thing for R, and his actions since I hooked up with R has been very... interesting to say the least. It is possible that he sold me out for her in hopes for (if he already haven't) sex with her. One thing I will take away from this is to always save numbers, you will save yourself a lot of trouble if you do so. I'm not sure if this counts as a white knight situation or not, but this whole situation is weird to me and I need some insight.