If it's shriveled all the way to the stem, I would say it's gone. (bows head for a moment of silence and sad ballad plays)
I don't think that the temps in the 90's and high humidity is to blame....
tomatoes are by nature tropical plants.....
I had both of my Olena Ukranian toms suffer from the same disorder..first the leaves started to curl, them the stems, into a twisted mess and then all started to turn brown and died.
Are any other plants showing signs of stress? Here in S.TX we too have
consistently hit temps in mid 90's and dew points in the 70's...
My toms are beginning to shut down production which is typical around this time of year when the lows are in the mid 70's and highs in the mid 90's.
About the only thing will continue to produce is my Tommy Toe and Husky Red Cherry...hardy little critters.
All other toms have huge amounts of large green tomatoes just begging for the heat to help start ripening.
Feed your soil and your soil will feed you