My question involves criminal law for the state of: california
My friend got put on unsupervised probation and ordered to drug rehab. He/she was assigned to 6 months, but stayed for a whole year. He/she has a medical marijuana card for real reasons, and is under the impression that california law no longer accepts marijuana as an 'illegal drug' anymore as long as a valid prescription is present. He/she has never been contacted, or come in contact, with any police enforcement and/or never been arrested for anything while on probation. He/she is going to college and trying to make a better life.
However, my friend(we'll call him dave), Dave, trusted the wrong people. Dave says some friends he hadn't seen in awhile(after somewhat unheartening experiences with them), and taken to an unknown house, where dave saw them all using their sweatshirts with the door handle, noticed no pictures on the wall, and then noticed a smell of marijuana in the air. Around this time, daves club card got stolen as well, and we can only assume its being used against him in some way. Me and dave can't figure out exactly what went on in that house.
Dave also think that they set up what seems like an incriminating photo/situation, when in fact it is the complete opposite.
My questions are these:
If a probation violation is in place, would the probationer immediately be contacted/detained? Could they wait to hold it against him at his court date(final court date)?
Is this even real evidence? My friend has never been caught doing anything illegal, thus never arrested, so what could a couple fingerprints on a door handle and a picture(which, btw, dave thinks was made to look like he was selling or doing drugs) really even prove? I know my friend is innocent, as i'm the only one who's been with him the whole probation time period, and I know my friend is honestly trying to make a better life.
How would one disprove this b.s.?
What's the likely outcome if a PV(whether or not it's fair) is in place? My friend is deathly scared of jail from bad experiences, and since they were originally on unsupervised probation, is it reasonable to think that they could avoid jail and just be on supervised probation?
Can a probation violation occur on any type of probation without ever being arrested?
And wouldn't a law enforcement agency detain/inform a probationer under suspicion of violating probation IMMEDIATELY, and not wait 6 months?
I greatly appreciate anybodies help! we're desperate.

