Why are you making this so hard on yourself?
Put the seed in the ground. Watch it grow.
Not sure what "I had to det the stem..." means. Not familiar with the term "det."
Although rinsing your root and laying it on top of the soil, exposed to light and air, has probably killed that poor plant. Now we will never know the potential of that bean.
If you want an easy method, get yourself some coco fiber. Saturate it, plant the seed, and check on it 3 days later. You'll have a seedling 99.9% of the time. Keep it happy for 2 weeks and transplant to whatever system you desire. It really doesn't get easier. All this paper towel, cups of water, etc, etc, is just a bunch of malarky. It is a shame those methods work at all because it is responsible for the stress of growers and death of many a fine young plant.
My suggestion. Plant it in coco. Don't baby it. Just let it do its thing. Shit takes 70 days to grow anyway... If you're having problems from day 1 I'm not confident the next 69 are going to be all that much better.
