The "cave"
I remember making that observation also. Orbital photos seemed to disprove the idea of a cave, but we'll know conclusively within two months I'd say. Maybe much sooner.
There's also a guy over on unmannedspaceflight.com name Ultrex who has named the possible cave area Ultrea Abyss. It's become kind of like some urban myth. After Spirit makes the dog leg turn on Haskin Ridge we should have a glimpse of the south face of Husband Hill.