Sorry to hear about Mickey's "supposed" regression.
In my experience, with our little chis being so small, it's more about not giving them the opportunity. Their world, their idea of the world is so much different from ours that, in the end, I think they perhaps default to pottying in the house because (let's be honest) the potty is so small, sometimes we don't catch it. I'm almost convinced that, despite my hawk-like vigilance, Ponyo has used certain areas for potty that I just haven't noticed.
Not to say anything mean about out beloved chis, but I don't think I'll ever trust my little girl fully in the house because... well... her bladder is just so small! And our "home" is different to them because it's so large. Whenever I can't keep 100% eye on her, I put her up. End of story.
Perhaps you started teaching again and he knows that you aren't watching? Hell, I'm a stay at home wife and sometimes I think Ponyo can sneak off.
With our dogs so tiny, I wouldn't take it as a regression. Any time I have troubles with my kids, I just go back to 101. It's really all we can do.
And kenneling for long periods of time isn't as bad as most people would have you believe... as long as you fulfill them when you get home and give them plenty of exercise and stimulation otherwise, 8 hours isn't unreasonable. If your kenneling at night as well, though, well... maybe that may be a bit much?
All I'm trying to say is that I train 100% of the time and every know and again I still find a suspicious stain... and I'm the only one to blame. But luckily Ponyo is comfortable enough in her kennel (and I shower her with kibble every time she goes in
) that just putting her in there when I can't watch her works best.