Someone I know missed a probation date because they were unaware of it. Will that result in a violation?

Just how were they unaware of a reporting date? It is up to the person on probation to be aware of their schedule of when to show up at the probation office. Has the person contacted their PO since they missed the reporting in? If not, they should do this immediately. And yes, it is a violation to miss your reporting date.

Yes missing any scheduled meeting is a violation. What the PO will or won't do is hard to say, But how did they not know, meetings are very well planned and the people notified.

Yes, it's a violation. Don't you hate it when someone you know does something like this?