Draw a picture, print out a post card, or buy a Get Well soon card, sign it, and have your Dad leave it in the room. Or put it in an envelope, address it to your mother's name, hospital's address and mail it. the nurses on the floor open the envelopes and put the cards on your mother's bedside table.
your dad just cannot cope with the mother's hospitalization, so you might as well cut him some slack. it is not fair to you and very unreasonable. you should totally be allowed to see your mom. it would be good for her - even the therapeutic touch. often people can feel their family's presence even if they are unconscious. but sometimes we have to cut people some slack, especially in difficult situations.
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Some of the threads I started are really long - yeay!