The same here happened to me, and you are correct, there is no magnet. I went into the vzw from the parking lot 5 times saying its not going into car mode. Then they would play around with it and it would go into car mode. I also didn't see a car dock app anywhere. This morning when I put my phone in, it didnt go into car dock mode, I pushed down a little harder and it did. It seems to be a hit or miss thing, which I am sure will be fixed in an upgrade, or at least I hope. Although the car dock app really isn't a big deal since its ugly as hell anyways, I mainly use it to watch tv while driving via sling box J/K... but, I mainly use it for maps and nav which is on my home screen anyways, so Im not that worried about it. Also, I didn't notice it at first, but the clip on the top of the car dock comes down over to clamp the phone in place.. I have no idea why sometimes it works and sometimes it doeesn't. So its either, you have to press down on your phone for a secure connection, or its software.. but now thinking about it, it may also be the way you have your car dock adjusted, maybe if you have it an upward or downward angle it messes it up but in all honesty I'm not sure...
Just noticing another thread now, this may also be the problem, calibrating the bionic. I swear I turned the phone in every direction but don't know if it worked or not, 1/2 the phone was green other 1/2 same color ...I'll play around with it some in a bit.