California DMV ripped me out of my parts.

There is certainly more to the story. ..or the backstory there of.

Do not think he didnt know there was a problem!

These things are - by law - proceeded by letters of notice for infraction, corrective/cease activity time frames, visits/attempted visits by enforcement authoritites, etc. Think about it, even code enforcment is required to send notification of violations 1st and provides weeks of time to comply/show compliance and under due process laws, a violator has the opprotunity to appeal violation, show legit cause/continuance and have his or her day in court.
They are not ever out of the blue (like a drug raid), unless there is a probable cause warrant - to enter said property, to confiscate evidence, etc, all issued by a judge. This would have only been granted after a lengthy undercover investigation that had aquired sufficient evidence to pursue criminal charges.
I can also tell you, they do not do so over 1 car or 1 infraction. ever.
Ignorning the attempted legal process(s), then leads to court action - which then normally involves a Judge, signed documents, lawyers, the PD, etc.
That is how things work, yes even in Calif.

BTW - if they found parts for more than one car (ie his 71 challenger) for sale / had been sold, during their investigation, that very well could cross the threshold for unlicensed wrecking yard. In some states, its as little 3 vehicles per 12 month period.

My guess ( based on yrs of LE experience) I would bet:
Your friend sold your stuff.
Your friend sold alot of car stuff without any proper license, land use permits, salvage yard EPA mandate compliance, state DMV, Highway Patrol & local authority inspection requirements, the list goes on.
All his cars being dirived from junk cars he was buying off craigslist, found abandoned or what have you.
Probably (as in 99% probability) some were missing titles &/or other docs proving ownership & title status. <- this is normally what causes a complaint/code violation to move to a criminal investigation, when it involves vehicles/ vehicle parts.
His back yard/property has the appearnace of a full blown self serve wrecking yard and the neighbors got tired of it.
These things are normally complaint based.
I'd wager he has ignored or refused to come into compliance as requested - several times.
This would result in authorities taking the above action and confiscating everything left, that maybe connected to the illegal activity.
and would be a far cry from some poor bloke selling an old bumper he had, on craigslist...