Was My Vehicle Illegally Searched?

I am currently living out of my truck. I was sitting in a multistore parking lot changing clothes for work. I have a sunshade on the front windshield an black cardboard for the other windows. I had just come from the senior center for coffee and parked when there was a knock on my window. I opened the door without a shirt to 2 Orange County sheriffs deputies who said hello and asked what I am doing and that they’ve seen my truck here before and they have a right to find out what I’m doing because it is private property. I shook one of the deputies hands and explained that I am homeless since July 17 when I was unlawfully evicted and I have not had enough money to find a place to live. At this time I noticed light smoke exiting the cab that was from the air conditioned air meeting the atmosphere and having excess moisture that turns to looking like smoke. I know the deputy noticed this also as he asked me to step out of my vehicle which I did. He said I’m not under arrest I’m just being detained. He searched me, handcuffed me and placed me in the back of their cruiser. He asked if he can search my vehicle and I said I’ve had too many things done to me so I do not feel comfortable having you search my vehicle

Both deputies went back to my vehicle and one of them leaned in and then they started tossing my truck and going through my toiletry bag and backpack. They came back and said they found a baggy with white residue and they know what stuff is do I want to tell them what it is and I said the only baggy I’m aware of contains ibuprofen for my pinched nerve and the pills were cut in half.

They went back to tossing my truck then the deputy mirandized me then took off my handcuffs and I was released with a citation for possession of meth and paraphernalia. I was never shown what they found, nor was anything tested in my presence

My question is did they have probable cause? And shouldn’t my vehicle be more protected since it is my home. Do I have a good chance to beat these charges?