The dog pushed the shifter into "L" as in D-4-3-2-L, right? L is just the first gear, so if you were going anything higher than 40km/h then the transmission wouldn't have gone all the way down to 1st gear. The high revs would be because the tranny downshifted to the lowest possible gear without redlining. The car just "stopped" but does this mean that all wheels locked up and you stopped completely and rapidly or does that mean that the engine shut off? The transmission doesn't downshift beyond the redline, so I wouldn't be too worried about the engine.
You may want to try shifting through the first couple of gears from a full stop to get a feel for the gears. From a full stop, shift into L and then start driving. keep an eye on the tachometer and accelerate lightly to about 3000rpm then shift into 2. If the transmission switches into 2nd gear the rpms will go down to somewhere between 1000-2000rpm.
What you've described sounds pretty normal to me except for the part where you say "and my car just stopped". Hope this helps and I hope your car's alright.
ps. It's a good thing your dog's alright too. When I started reading this thread I saw the title "Why?" and thought your dog jumped in front and then jumped out the window!