What are the growing conditions? Do you use heat? How often do you water? Do you keep them inclosed in a mini greenhouse/plastic dome? What kind of soil or mix are you using? What are you using for a light source?

Mark

I don't take measurements for exact conditions. I sprouted the seeds on top of my T.V. in baggies. It was the warmest spot in the house. They actually sprouted a root fairly quickly.
The house was kept at least 71 degrees most of the time but the T.V. vents were much warmer. I put them into soil shortly after I saw a root. Just under the top of the soil. I would moisten the top of the soil if it looked dry. Really I would re-moisten it any time it looked dry. The containers won't sit on the T.V. so they get sat in either an east or west facing window sills as these are the next warmest spots in the house here in AZ, still they get cool at night. Most are kept in gallon zip lock bags to simulate a green house.
I'm thinking that from now on I will let the seedling get much larger before putting it in soil.

So does the disappearing seedling happen for a variety of reasons?

Two things could be causing an issue. If seedlings are left overnight and it gets too cold at night on the window sill and they die. Second cause, if you leave them after they sprout in a gallon ziplock bag there is no air flow, build up of moisture/humidity then damping off sets in and kills them quick.

Once they break the soil take them to a light source with plenty of open space/air flow. I would keep them out of the ziplock bags or mini greenhouse systems at this point.

When placing on the window sill if at all possible take them down at night then place them back during the day.

Mark

Okay, will give another go soon.