During all the confusion and investigations when the package was found, surely someone within Old Trafford must have been aware of such a drill taking place mid-week and would have let someone know "Hang on a minute. That's from the security drill from Wednesday. Just lob it in the bin". The amount of media coverage it was getting, if someone was involved in that drill midweek but wasn't at Old Trafford today, one phone call would have cleared it up.
Would nobody have thought it was a bit of an unbelievable coincidence that staff at Old Trafford were doing bomb security drills on Wednesday, and then A MOTHERfeckING BOMB appears on the next nearest match day?
Come off it.