Bizarre yeast behavior

I tried making my own slants by making a starter then pitching only about 2/3 of the starter for my next batch, restarting the starter with some fresh wort and then freezing the slurry in a glycerin solution. See this blog post.

I pulled my first slant from the freezer, defrosted it and made up a new starter from the defrosted slurry and then brewed my favorite Irish Red and pitched the yeast on Saturday morning. The fermentor sat in my basement where my wife accidentally left the exterior door ajar on Saturday night (it was cold outside, so the basement temp dropped to about 62). Needless to say, there was no visible fermentation (i.e., no bubbles in the blow off tube bottle) on Sunday morning (24 hours post pitching). I closed the door, bringing basement temp to 68 and by Superbowl time last night (hurray Ravens!) the blow off was chugging along, but very gently (usually I get a pretty vigorous bubbling in about 12 hours). This morning (48 hours post pitching) no more bubbles. I gently agitated the fermentor and got no additional activity. Tonight I checked the gravity and this is what I got:

Original Gravity using a refractometer was 14.1 (1.057). "Final" Gravity tonight was 6.5 (1.006 with correction calculator). I guess it's possible the yeast went crazy last night when I was sleeping, but there's not even evidence of krausen.

What happened? Did I just get a very rapid and highly attenduated yet very gentle fermentation? Any thoughts?

Apparently you slanted some very hungry yeast! Complete fermentation in 48-60 hours is not unheard of. Also starting it out cool and then warming it up probably really got it going. Sounds like you had a great fermentation. Should be a great beer!