Didn't see that one myself but now I'm gutted I missed it. I'm up in Inverness so obviously not going to spot a Phoenix sighting but I've been following the triangle UAP stuff really closely lately.
Can I ask - was it a solid object or more like three separate lights keeping formation? That distinction seems to matter a lot when people try to explain these away as conventional aircraft. I've read a few reports where witnesses describe a kind of faint membrane or darker mass connecting the points and I'd love to know if that matched what you saw.
Also did it make any sound at all? The silent ones are the ones that really get me. Conventional craft that size would rattle your windows.