I wish I knew how easy it would be for a feature like the dot to break off accidentally. I can envision a situation where the plates were removed from the press because the printers thought that the run was finished, and then maybe they realized that they goofed up and were 100,000 covers short—or maybe D.C. called in a last minute increase to the size of the order—or maybe some covers got ruined and they had to set everything back up to run more covers.
Any extra handling of the plates could have led to extra wear and tear, which could account for the missing dot and the ink bleed.
Maybe they ran part of the order on Friday, shut down for the weekend, cleaned the old, dried ink off of the plates before they started up again on Monday, and were a little too rough with their cleaning.
I have a hard time seeing them interrupt a print run just to address the issue with the dot on a 10-cent funny book.