The filter search works in combination with the filter panel. Currently, if the user enters the search field and presses "esc" key, the panel gets closed, but since the text input is still active in the search bar, the user reaches an inconsistent status: the user can keep typing but no selection is possible since the panel is gone and cannot be made appear again (unless the user exits and enters the field again).
Making the "esc" key to remove the input focus from the search field (in addition to closing the panel) would solve the issue.
This is a minor glitch, so feel free to prioritise it accordingly.