I've noticed that my brain, in the presence of alcohol or allergy medication that causes drowsiness, tends to retain information similar to footprints in sand getting washed away by the waves.  The imprint is still there, but the full context disappears.  I'll have entire conversations or read chapters of books, only to think back on it and simply recall that the activity happened, not the information contained therein.  This can be bad because I might say things I don't remember, and then get called out for saying something dumb.  But it can also be good because people talk too much, and I don't need that stuff clogging up my processor.