Thank you OP for posting your experience and your frustration.
Thanks everyone for posting your opinions on why it happened.
I, for one, have learned something new here on the boards AGAIN!!!
Been to WDW multiple times. Have given up the commando style years ago so have not been at many park closings over the past 6 years. With young children the last few years, we've had early hours. We have attended a few special ticket events during that time but aside for finding out any discounts and the early admission (have APs anyways) here on the Dis, I don't know all the ins and outs. Since we had kids and no longer do commando style, I really don't do a park strategy anymore (gasp!) - more of a go with the flow tihing - although, I do have to pick a park for which day especially if I want to plan around ADRs.
We aren't park shoppers so we don't spend a lot of time "fighting the crowds" in the stores at park closing. But when we are at park closings we do stroll at a leisurely pace out the door and notice everyone doing that last second shopping with the insane lines.
WITHOUT this thread, I would have NEVER known about the "hard" closing for stores during special event evenings. It might not have dawned on me to even make the connection especially when I see many people in the stores but I would hate to tell someone the wrong information or be faced with unknowingly trying to buy that one item I wanted on our LAST evening before heading home and THEN finding I couldn't do it due to poor pre-planning on my part.
Now that the OP has "vented" his frustrations on his experience and learned about the reasons behind Disney's current policy, hopefully he understands why things happened the way if did and feels better even though he probably feels that the CM and/or WDW could have handled things a bit better.
His post on his experience has probably "helped" lots of people here on the Dis from making the same mistake. Now Disers that will be in the parks on the days of special events will know the current policies of the store closings and can now factor that into their planning so as to NOT break any of those polices.