All mine are finally up.. Planted 8 plants this year and have a 3 year old Centennial that's doing quite well with 2 bines up about 6 feet. The new plants are all very short, most aren't even long enough to train onto their ropes yet. It hasn't been real warm around here yet - I'm expecting they'll take off once the sun starts making regular appearances.
One of my plants has an exposed root bulb like that as well. I think the soil settled or got washed away in a heavy rain or something. no harm to the shoots, all looks good, so probably nothing to worry about on yours.