I have a different opinion Re: hair loss selenium mystery
If I understand it right, 1200 ug is 1200 mcg, and selenium one time dose of that would not be toxic. However if you have taken a lot of selenium over a period of time, that and hair loss might be related. I am really bad at taking supplements and often take 600-1000 mcg selenium a couple of times a week, often more, (supposed to be good to slow diabetic retinopathy and macular degeneration). I may be more toxic than you, and heavier, but if you have not been taking more than 500 mcg daily for a long period of time, I cannot imagine that one 1200mcg dose would put you into toxicity. There was a study done on rabbits and rats where they considered therapeutic doses of selenium to be 0.5 mg per kg of weight - that is really high! There was a guy who took 10 GRAMS that died:
http://www.mja.com.au/public/issues/186_09_070507/letters_fm-3.html
but that is a far cry from 1-2 mg.
I believe that hair loss is not related to what you have done that day or two, but more as to several weeks before, as it takes time for the hair to "die". An exception would be if you applied chemicals. I think it might be from the detox you experienced last week, and if so, you will see a thickening of your hair again in a few weeks. My hair has thickened and thinned and thickened again over the years, and I find that keeping the oil build up off my scalp (contrary to my mother who washes her hair once a week) and I have to shampoo every day, massaging the scalp, especially hairline, well.
So even though hair loss is a symptom of selenium toxicity, I think it would have to have been toxicity from a week or two or three before.