Steps to reproduce:
1. Download attached project
2. Open the project
3. Create a scriptable asset with Assets/Custom Assets/Conversation
4. Exit Editor
5. Open project again
6. Inspect the created scriptable asset

Expected result: asset retains data
Actual result: asset data is invisible and unuseable

Reproduced on 2018.1.0a1, 2018.1.0a3, 2017.3.0b9, 2017.3.0b1, 2017.3.0a1, 2017.2.02p1, 2017.2.0a1, 2017.1.2p1, 2017.1.0a1, 5.6.4p1
Not reproduced on 5.6.1f1, 5.6.2f1

Notes:
- Having the asset selected and entering playmode makes the fields visible again
- Until the above is done, the assets cannot be used in scripts
- The data is still retained, but the asset becomes temporarily unusable
- Does not happen to assets in use in open scenes