Most Sample Editor functions are destructive, changing the files stored on your hard drive. You can, of course, use the Undo feature if things do not go your way.
Choose Edit > Undo (or use the corresponding key command, default assignment: Command-Z).
Press Command-Period.
The audio file will be retained in its original state, even if it appears that a portion of the editing function has occurred.
You can configure the Sample Editor’s undo functionality in the Logic Pro > Preferences > Audio > Sample Editor pane. For details, see Audio Sample Editor Preferences.