Andlyn, I know it feels like a big deal and you have every right to be worried, upset, nervous, and pissed off. But YOU did nothing wrong so don't sweat it. I don't know the ins and outs of how things work in Cali. but I'm pretty sure even if you would have gotten pulled over, the law enforcement wouldn't have known that there was a paperwork screw up. And even if they did, and ATF was called or something, you still did nothing wrong and they know that.
Short story. I sold a rifle to a buddy of mine (I'm an FFL). He filled out the paper work, I called it in, they told me it was "Delayed" which meant they needed to look into something. Here in Texas, if you don't hear anything back from them in three days you can proceed with the transfer, so I did. About a week later my phone rings and it was the ATF. Apparently someone was suppose to call me back with a "Deny" response and never did. Now you want to talk about being nervous? I had to tell them that I had already transferred the rifle. I thought they were fixing to lower the boom on me. But they were really cool about it. They just wanted to know where he lived so they could send a Sheriff Deputy out to pick it up. It turned out that my buddy had a pending court case in another state. All in all, everything turned out and he got his rifle back.
I guess what I'm saying is that mistakes are made on all levels, and the ATF are NOT the bunch of jack booted thugs they were once made out to be.