I'm not sure that someone simply saying ''I am sorry'' with no further words or explanation is ok. I am thinking of one example in particular from my life .... again, someone who was supposed to be somewhat ''close''.... but, maybe this person meant he was sorry. (the person I used to have a ''relationship'' with probably did not have much empathy or other qualities which would make an ''I'm sorry'' genuine) It depends a lot on the tone of voice, and other stuff, as I'm sure you know (and sorry this message is rushed, its long past my bed time and I have other things I need to do which I have been putting off tonight) Hugs and much respect to you