"Remember Chicago" Transformers 4 Billboard

Sam Nickelson, a member of Michael Bay's official Shoot for the Edit forums, has posted an image of a billboard from near the "Transformers 4" filming in central Texas that reads "Remember Chicago". This of course is a reference to the destruction of Chicago in Transformers: Dark of the Moon. The billboard also says "Report Alien Activity" and gives a phone number. Check it out mirrored below.