Thankfully, since when I made this post, we have not had any peeing in the house incidents. Honestly if he had not peed in the house that one night, I wouldn't have any inkling that anything was wrong. I've been trying to watch the colour of his urine but it will go from clear to yellow then back to clear, so I don't always trust that as a barometer.
He is neutered and I am wondering if there's not something related to that, but more specifically I think it's because he was cryptorchid. The doc I used at the time made it sound URGENT that he was neutered right away. I put it off as long as I could (with her breathing down my neck that it was URGENT) and he was neutered at 8 months, earlier than I would have liked for sure. So she had to go digging around to find his undescended testicle and I wonder if that didn't do something that we are dealing with the fallout of now. He doesn't leak though... we had issues with peeing in the house last year when he was still running around with those six bladder stones rumbling around, but since then we've only had this occurrence and one other time: the evening after the day he was squatting but wasn't peeing, I came home and flushed him with dinner, and he was downstairs sleeping, woke up, stood up, and peed out a TON of water. =P
He had full blood work done before his cystotomy last year; Doc doesn't think it's his kidneys because nothing on the blood work indicated anything going on there. Doesn't mean nothing is going on there of course, but I would think that would produce the same problem rather than his pH being low one time then high the next and all over. The fact that he is not having an exact re-occurrence but instead just persistent problems of one type or another that all happen to be bladder/urinary related is what makes this so frustrating... =/
I'm not gonna look too far into possible causes right now since the first one I saw said CANCER and I'm going to pretend that's impossible and Auggie is immortal.