ESB 1968, is a really forgiving yeast strain. CO2 is heavier than air, so unless you blew into the blow offs, I wouldn't worry. Besides, when fermentation restarts the CO2 being generated will keep your wort safe.
Oh, right, stop being paranoid, your beer will forgive you. I have accidentally cold crashed a batch or two of 1968 and the wort warmed back up, the yeast got busy again. At 1.020, there won't be a lot of activity, so don't freak out. I have an Amber ESB conditioning/cleaning up in my living room. I brewed it on 2-12-2014, and held it at 64* F for two weeks, warmed it up during last week. As far as swirling goes, I always swirl my fermenters 3 or 4 times a week. I know from experience (the hard way) that there is generally a little CO2 trapped in the trub after fermentation has completed. I continue to swirl my fermenters until no more bubbles are released, and then cold crash for a minimum of 6 days at 34* F. My beers are clear and tasty, and for that I am willing to wait an "extra" week or 2. Right now my pipeline could use a couple of quickey beers so I won't be "chomping at the bit"to drink what I "just bottled" too soon. Sorry for the long post, I forgot to take my ADHD medication this afternoon. The truth is, I am very passionate about this hobby of ours, and hope maybe I will say something that may help someone else sometime in the future, like so many things that were said before I brewed decent beer that really helped me.