What does possession of stolen property or called theft by receiving carry?

The bill of sale is important since you are saying that you did not know that it was stolen. Lack of knowledge is a defense.

A violation of California State Penal Code Section 496 Receiving Stolen Property can be filed as a misdemeanor or as a felony. 496. (a) Every person who buys or receives any property that has been stolen or that has been obtained in any manner constituting theft or extortion, knowing the property to be so stolen or obtained, or who conceals, sells, withholds, or aids in concealing, selling, or withholding any property from the owner, knowing the property to be so stolen or obtained is guilty of receiving stolen property. If charged as a misdemeanor the punishment shall be in a county jail for not more than one year. If guilty of a felony the punish is imprisonment for 16 months, two years or three years.

The prosecutor must prove that you "knowingly" possessed or receive stolen property. The bill of sale should support your position.

At some point your public defender will get in touch with you. Be patient. Plead not guilty.

There are obviously a number of questions, you may have a bill of sale but did you receive the title to the truck? How did you get a plate for it or ensure it? Generally, if you innocently received stolen property you're not liable however, as the thief cannot transfer good title you will have lost your money and have to seek recovery from the thief with the property being returned to its rightful owner. Continue to attempt to get into contact with your appointed attorney and, I would advise, that you should not be discussing this matter either in a public forum such as the Internet or with anyone else until you're done so.