Part 1:
Reproduction steps:
1. Open the attached project
2. Click on the "Foo" menu at the top toolbar
3. Click on Select

Expected: the "Foo.asset" is selected and it's serialized fields are shown in the inspector
Actual: the "Foo.asset" is selected, but the inspector is blank

Part 2:
In addition, Resources.LoadAll<T> does not find the saved asset. (this happens on all tested versions)

All of this is caused by HideFlags.HideInHierarchy;

Fully reproducible on 5.5.0f3
The first part is not reproducible on 5.4.3p3 and 5.6.0b2