The Limited Capability for Work questionnaire is for ESA, as you are in hospital you are automatically determined to have Limited Capability for Work and there fore meet the criteria for the Work Related Activity Group.
Most hospitals have a welfare worker and it may be them who completed the form for you, however, they should have done a much better job of explaining what they were doing, a nurse should be able to ask the person to visit you again so that you can ask any questions.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems