Going to have to make up your mind. Either it's a 4 inch 'portion' off the top of the plant, or the bottom part that's still in the ground. Can't be both unless it was 4" tall. If it was a 4" tall youngster, it's toast.

Since you mention the hollow stem, tho...it's really impossible to understand what you're trying to ask, since a seedling doesn't have a hollow stem (it's 'hollowness' develops with maturity) you'll have to clarify what the heck you are talking about.