did i seize the engine???????

[booninety]

Can anyone help?? I have a 2001 X5 3.0 with 105k miles. It was very cold today and I didn't take it for my usual 35 mile commute, so I decided to warm it up when I got home from work. Started up with no issue, except it sounded a little rough, but that was normal in really cold weather. after about 15 minutes I went out to see how warm the engine had gotten and noticed the SES light came on. I thought perhaps I should move the car as it was parked on a slight incline in my driveway. That's when it rattled a bit and stalled. I tried to start it and it wouldn't start. I left it for about 10 minutes while I went to call my mechanic. The interior lights came on so it wasn't the battery, but it couldn't engage or turn over. I noticed just before it stalled that there was a huge cloud of white smoke at the exhaust. I checked the exhaust pipe for oil and there was oil residue. ANd since I was able to back up a little, I then saw a puddle of oil in the driveway-about a half a quart worth. There was no oil level warning light prior to this. Could I have siezed the engine? Or is there enough intelligence built into the onboard computer to shut the engine down so as not to cause any more damage?
Any information anyone can provide would be greatly appreciated. I'm going to sell my beloved X5 as I cannot stand having to worry that it's too cold to use my car!