"Un-mucking" a mucked hand

[WoodPaneling]

I was at Foxwoods the other night and a situation came up that I think was extremely questionable, was wondering how you guys would feel about it.

There was a 4 spade board, including the 4, 5, 6, and 8 of spades. Two older ladies went to showdown, one of them flipped some high spade, and the other showed the table her 7 of spades, made a :/ face, and mucked face down, obviously thinking she only had a 7 high flush. Dealer swept her cards into the muck and actually put the muck pile onto the deck and started squeezing the cards into a clean formation.

Someone decided that NOW they'd speak up and yells out "7 spades, she had a straight flush!" and the dealer grabs what seems to be a totally random card from the deck without looking and miraculously tables the 7 of spades. She then pushes the pot to the woman who mucked it, while the woman who showed the high spade just stared at the floor (as in the ground) shaking her head and looking absolutely crushed.

First off, she mucked her hand. Shouldn't it be dead the second it touches the muck, unless swept into the muck by dealer error? Second off, it wasn't even clearly identifiable in the muck, I have no idea how the dealer managed to table that card. And also, don't you have to show both cards to win a pot at a showdown? I believe she flashed her other hole card prior to mucking but it wasn't involved at all when the 7s came out. This just seems really ridiculous to me and I think the woman who didn't muck should have gotten the pot.