My nightmares make more sense than this situation does.
Today, I confirmed that DMV has no record of a REG 138 form that would transfer liability into my name. So the REG 138 that FasTrak has (with my name as the buyer) is a complete fraud.
I don't know what is going on, but have some theories:
1) The registered owner is a criminal, and still has the vehicle. He gave a fake REG 138 to FasTrak with my name as the buyer on it. He crosses the bridge twice a day, thinking he can fool FasTrak and get them to blame me.
2) Same as 1) except the registered owner has a pair of fake plates that he uses just when he crosses the bridge, just to make the story more interesting.
3) The registered owner is a fool who sold the vehicle to a buyer who is a criminal. The buyer never went to DMV to complete transfer of ownership, but started crossing the bridge twice a day, thinking he can fool FasTrak and get them to blame the registered owner. FasTrak sends the bills to the registered owner, who then is told by FasTrak he needed to file a REG 138. The registered owner doesn't know the real name of the buyer, so he commits fraud and identity theft when he writes my name down as the buyer on REG 138, and delivers the form to FasTrak to get them off his back.
4) Same as 3) except the buyer really has the same name as me, but the registered owner doesn't know his address. The owner finds my address in the phone book, and is stupid (or evil) enough to use it as the buyer's address on REG 138, and delivers the form to FastTrak. I know there are at least 6 people with my name living in the area.
5) Same as 4) except the registered owner is old and got someone else (like a daughter or a son) to find the address. They found mine and used it on REG 138, gave it to FasTrak, etc.
6) The fraud is happening at DMV to allow someone to cross the bridge without paying.
7) The fraud is happening in FasTrak/ACS to allow someone to cross the bridge without paying.
8) Same as 7) but there is no vehicle with this license plate crossing the bridge, and FasTrak is just making this all up to rip-off citizens like myself.
9) The truth is too strange to even imagine right now. (The most likely scenario!)