Here is what I found on Flannel vs. Flannelette (not usre if this helps or not, cotton flannel usually shows the weave on the back of the fabric)
Flannel is a soft woven, of various fineness. It usually doesn't have a nap, and instead gains its softness through the loosely spun yarn it is woven from. It is commonly used to makeclothing, bed sheets and sleepwear.
Flannelette is a light, napped cotton the texture of flannel. The weft is generally coarser than the warp. The flannel-like appearance is created by creating a nap from the weft; scratching it and raising it up. Flannelette can either have a long or short nap and can be napped on only one or two sides. It comes in colors, both solid and patterned.