french.about.com seems to suggest that either savoir or connaître could be used in this sentence.
Savoir or Connaître
For some meanings, either verb can be used.
1) to know (have) a piece of information:
Je sais / connais son nom.
I know his name.
Nous savons / connaissons déjà sa réponse.
We already know his response.
I believe savoir is mostly used when you learn a certain knowledge or a topic, mostly things that are taught in school, like maths and such.
Connaître is similar, but not the same, for people and places, this sentence in particular could merge both ideas (Details of a person perhaps, maybe in a crime scene suspect, just an idea)
What I always do is to read the sentence many times then ask myself, is this knowledge (savoir) or could it used as a resemblance for someone or somewhere (connaître) ?
Since we don't know for sure in this one.. I don't think using either would turn into a problem, unless a hint of context is given.
I don't think so. To not know is to genuinely not be aware of something, to ignore is to be aware but not care about it. According to Wordreference "ignore" is "ignorer" or "ne pas tenir compte de", or possibly "faire semblant de ne pas voir".