There are at least two ways the police can lawfully hold a vehicle. The first is if it is evidence in the case. To determine a valid evidence hold, a lawyer would need to be familiar with the facts of the case. Typically, if it does not qualify as evidence, it may be released at the end of the case. That unfortunately can be many months or even years. In some cases, a lawyer can negotiate certain evidence issues, such as agreeing to the substitution of photos for the vehicle. Then the car may be released.
The second valid hold is based on forfeiture law. The police can seize, hold and then attempt to forfeit a vehicle (to the seizing government agency) if it was used during the commission of the drug offense or if the vehicle was purchased with drug money. An innoncent owner of the vehicle may have a claim. However, any claim for return of a vehicle the police are trying to keep via forfeiture must be made within 45 days of the notice of forfeiture. An attorney should always be consulted in a forfeiture case.
This is a very complex question. There are several legal ways an officer can arrest without a warrant. For example, if a crime is committed in the officer's presence, an arrest normally does not require a warrant. (e.g. a DUI arrest). Also, if the officer has information from other officers or reliable sources that meets a probably cause standard, then an arrest for a felony and some misdemeanors can be made public. On the other hand, if you are in your residence, then the police cannot make an arrest without a warrant or consent by you or another resident to enter the residence, unless it is an emergency.
As for searches, a search of your person pursuant to a legal, warrantless arrest is usually legal. However, if you are placed in the squad car, they cannot search your vehicle (without a warrant or consent) unless there is a risk that evidence could be destroyed or there is a safety issue. If you are just stopped by the police on suspicion, they can only frisk you for officer safety. If the police basis for suspicion is not supported by sufficient facts, then the frisk may be illegal.
No. For starters, the State has 3 years from the date of the offense to file a felony drug charge. Secondly, the crime lab is backed up, and prosecutors frequently wait for lab confirmation of the drug before filing a case. That can delay a filing for as long as a year. The only way you will be informed of a charge is either by a summons or a warrant for arrest, or both. The summons will be sent to the last address you gave the police and court when you were booked and/or brought to court. If you have moved, you should contact an attorney who can contact the prosesutor.