I know for fact my signature was forged on a bill of sale for a vehicle. The buying party also knew my signature was forged as it was done right in front of them. Can the buying party also be held accountable for the forgery though I lost no money nor gained any money.
It's hard to say. I think the forged signature might not be a crime by itself, but whoever did this had some reason - instead of a sales agreement that states (with signatures) that Mr. X sold a car to Mr. Y, there is now an agreement that states (with forged signatures) that Mrs. Jones sold a car to Mr. Y.
I could imagine that somewhere along the line some crime has happened and the forged signature is used to obscure the crime. We'd have to know what exactly happened. (For example, if Mr. X was your ex-husband and the car was your car and your ex-husband kept the money from you, that would quite clearly be a crime, but you said you lost no money).
Forgery is typically a felony; but it's not certain that the act in question satisfies the requirements of a forgery statute. In Washington, that is RCW 9A.60.020. Signing another person's name is not necessarily forgery. First, there has to be an intent to injure or defraud, then the document must be "falsely made, completed, or altered". That in turn means "to transform an incomplete written instrument into a complete one by adding or inserting matter, without the authority of anyone entitled to grant it", thus you can sign on behalf of a party with their permission; if you have pure intentions but no permission, it still is not legal forgery. It is possible that this violates a vehicle-sale specific law, RCW 46.12.750, since the bill of sale may function as an assignment of title for purposes of obtaining a certificate of title. The requisite form in Washington doesn't have the perjury warning that you find in California, where the signature is more meaningful. So it would depend on your jurisdiction.
It's not clear whether anyone was actually harmed by the act (which I take to have been signing your name to a bill of sale). Some actual harm would be required, in order for there to be a successful lawsuit. Criminal prosecution is possible (but unlikely) even if there was no harm.
It sounds like this is in the USA, so I'm going to assume that.
If I understand you correctly, the Forger needed your permission to sell the vehicle, but couldn't get it. The Forger and the Buyer have therefore entered into a conspiracy, probably a criminal one as it sounds like the forgery itself was a crime.
The Buyer does not have good title (and wouldn't have good title even if they were unaware of the forgery). If you have a part share in the ownership of the vehicle then you still have that, regardless of any money you may have been given. You can probably sue for the return of the vehicle. Given that the Buyer does not have "clean hands" you probably even get to keep any money you were given.
Also if the Buyer knowingly uses the forged signature to prove title to someone else then they are probably guilty of a separate fraud at that point.