The repro case is to create a material with a texture (texture T), apply it to some object, like a basic cube.
Save out this level, level A.
Create a new level, and add level A as a sublevel, and save this level, level B.
When I reload the Editor, and load up level B and open the texture editor for texture T, it shows that the Import Settings are not there.
However if I start up the Unreal Editor and load up texture T by opening the texture editor immediately, or load up level A, and open the texture editor for texture T, the Import Settings will be there.
This must be something to do with streaming and textures, as other asset types loaded in the same manner load up correctly.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-23835 in the post.