Ok here goes, i was on a sat. night enjoying myself watching the local street races from in a factory parking lot when a cop flashes his siren and pulls a car next to me over so i decide to leave my car there and go in another friends car and come back untill they left and I did and the police car was still there so i go to get my car thinking he won't say anything and fearing he will tow it if i waited any longer, and his backup's car is blocked me in and i find somones dirty pair of shoes and food wrappers in my car that wasn't mine and the cop said he threw it in my car (because my windows where left open) and he also told me that i had a spare key in my glove box and i asked him how he knew that he said because my window was open and he unlocked my car and went in the glove box and searched it. also on top of it he gives me a ticket that says "SIMPLE TRESSPASSING" Now is anything that the police officer did illegal and is me being in a factory parking lot considered tresspassing or are there certain exceptions to that. please let me know thank you

Note: i didn't take any pictures for evidence but I have a witness that heard what the officer did and saw what he did

Is it illegal? yes. But it could be legal. Depends on factors.
If you are on property illegally as a trespasser and you are on private property, unless they have an open public invitation for the races, you are technically tresspassing. As for the open window, police can use the plain view doctrine to search a vehicle that extends to things visible in the car. But your windows were down, thus they might say the car was abandoned on private property on which you were trespassing and they entered the car to perform an inventory prior to the car being towed away back to their towing contractor's garage. If this is happening in a public space that is regularly used at night for the purpose that you were there, then the answer changes. They can investigate based on the plain view doctrine, but the keys were no in plain view, thus their discovery and being in the vehicle was illegal, unless it is an abandonment situation then entry again may be for inventory prior to writeup to call a towing contractor.
So that is how I think this might be argued. They probably thought you had drugs.

So how would i know what is private property and what is public property? would a no tresspassing sign have to be posted on there property or a private property sign? Are you allowed to be on public property at anytime without it being considered TRESSPASSING? Does the officer have to tell me why he searched my car or if he was going to tow it because he didn't tell me why he searched my car . Is it illegal for them to put objects found on the ground and into my car? What should I do to fight this ticket that I was given? take pictures or can witnesses be used in traffic court? Does a non-moving violation like the ticket i got affect my insurance or points on my license? please help me answer these questions, Thank You

Note- the parking lot was not used for racing it was used to park my car it was right next to the road where the races were going on