A stuck sparge shouldn't be anything that takes more than a few seconds to correct. If you are draining your mash tun with a hose attached, just lift the hose about the level of the mash, and then blow into it until bubbles come through the mash. In my experience, this fixes it the first time probably 95% of the time. If it doesn't fix it, do it again, but blow harder. You can also use an air compressor, but it's quicker and easier to just blow into it (remember, it's pre-boil, so you don't have to worry about contamination).
Normally yes. If you're counting on it to drain in your absence while measure out all hop additions or whatever it was that I was doing at the time, then it'll hit when you're not looking. Literally. Come back to see the hose not dripping and the tun still plenty full.
Turns out a watched pot will never boil and an unwatched sparge will never drain.