I used to think phone shots of the moon were pointless, then a guy at a star party in Sedona proved me wrong
He handed me his phone clamped to a 6 inch dob and said "just hold still for two seconds," and the shot of Tycho's crater rims that came out made me delete my whole folder of DSLR moon pics that never looked half as sharp.
Did you have to mess with any settings on the phone or did you just let it do its thing? I had almost the same thing happen to me last fall when a buddy let me try my phone on his 8 inch scope. I just held the phone right up to the eyepiece by hand, no clamp or anything, and tapped the screen to lock the focus and drag the exposure way down. Took a few tries because my hands kept shaking but once I got one steady shot the craters came out way better than anything I ever got fighting with my old camera and tripod. The big thing I learned is you have to turn the brightness down a lot, because the moon is so bright the phone wants to blow the whole thing out into a white blob. Turned out the phone did fine and I was the problem the whole time.