في نعمة
In blessing; that is, in a condition of blessing.
The phrase shows that “fī” is not confined in usage to a physical object inside a physical container. A condition can be conceived as something surrounding or embracing its bearer.
A rhetorical explanation relates physical containment to being enveloped by a state. The particle's use then follows that understood relation. This does not make every nonspatial use automatically the same species of metaphor without further examination.