I posted a feature request for this and its been marked as implemented. Perhaps I didn't explain it too well and I hadn't noticed that tiny little circle on left side of the search field.
But I'm really asking for a real button labeled "Clear" and situated above the search field. It would clear the search field AND restore the contact sheet to what was there before. In other words, it would UNDO the search.
I feel that would be useful, intuitive, and be consistent with what we have in the Filter and Browse panes?