Toni, I bet that did spook your poor mom! I wonder if this might not be some sort of residual energy? There have been times I have sworn I've heard my husband's footsteps on our porch, only to look out and no one was there. It certainly is strange!
Did your mother get a good look at "whoever" was sitting there, or was it just out of the corner of her eye and she assumed it was him?
Glad you are feeling better! Hospitals aren't fun places to stay!