Physical assault by McDonald's for wearing Digital Eye Glass
No one at an ordinary McDonald's would even notice such a device.  Ergo this was not an ordinary McDonald's, but one with security people looking for cameras.  Why would a McDonald's have security people looking for cameras?  Possibly because it was a mafia front. If you wanted to launder money, a fast food restaurant in a popular location would be a good place to do it.The way the employees behaved is consistent with this explanation.Edit: I should have said no more than that the excessive reaction of the security people suggests there may be something dubious happening at this McDonald's that they don't want filmed.  But there are other less dramatic things they might be doing besides money laundering: using undocumented labor, for example.