Blow off at 12 to 20 hrs

So, I brewed AHS Pumpkin Spice Ale last night. Checked on it this morning bubbling away like crazy. I have a 3 piece air lock on there, With a very thin sheet over the bucket and air lock. (I can feel the air coming through the sheet). After work (about 20 hours after yeast pitched), I check on it, and a blowoff happens. The sheet is still covering the bucket. I put the lid back on. It has been 4 hours since I reattached the lid and no fermentation bubbles at all...


Thoughts? Did I loose a batch?

What are you concerns exactly?

Concerns are that it's contaminated and it won't ferment out completely

Probably not... you will be fine

So your concern is that the lid popped its seal? There's absolutely nothing to worry about. Many brewers have had their fermenter lids blow off and spray beer all over the closet or garage while they are at their mother in laws for the weekend, the beer sits there for two days with the lid off, and the beer turns out fine.