Arcane and hiding in plain sight

If a person has Arcane do others ignore him or her like that person is not even their?

That is obfuscate. Arcane is a bit different in that it represents the world having trouble remembering who you are. People who meet you briefly will forget your name, what you look like, what you were wearing. They will only remember the vaguest of details unless you have obvious deformities, such as a missing arm. It also applies to the world in general. Records of you tend to go missing, or become unreadable.

How this might be seen in an example could be: Walking down a street with guards looking for someone matching your description. They will overlook you because even if you are like that they won't notice/remember. However if you are walking down the same street where the guards are enforcing a curfew, they will stop you because they are stopping everyone.

Hope that helps, I don't vouch for it's accuracy until the STs agree/disagree however.