I had my engine blow on my first M3 (2011.75) at 12,XXXKM...a few days prior my car got stuck in a massive puddle at the car wash and wouldn't turn over...after about 20 minutes of being on the phone with BMW Assist it decided to start and go right through the puddle. Gave her a wash and took her home. Drove fine for about 3-4 days, then I went on a pretty long road trip (300 or so KM each way not including city driving and pictures of scenery with the car), came back around my home and went to the same car wash...one the way home from there which is like 10 minutes, I was doing 120~kph and then BOOM! Cylinders 3 AND 5 shot right through the block.
Needless to say it was covered under warranty, reason being, they didn't give me my break-in service till 4,XXXKM...totally their fault, even though it probably had nothing to do with that anyhow. If I was you, which I was at one point, I would fight for a whole new engine...don't let them re-use the block. I ran my new engine for 60,000KM in 18 months (I drive a lot...) and didn't have a single problem after that. Traded her in, didn't lose a dime on the resale and picked up a 2013 simply cos it was the last E92 on sale in Canada and it is a Fire Orange.
Good luck, hope I helped in some way.