There are several steps to take to get the spinach back.
You need to fill a large bowl with cold water and ice cubes to get the water cold.
Put in 1 tablespoon of salt per quart of ice water.
In a separate large bowl, fill with very hot tap water.
Place the spinach in the hot water for approximately 5 seconds, then remove.
Please then place the spinach immediately into a dip of the cold water.
Swish it all around for about 15 seconds.
Take it out and blot with a paper towel while draining in a colander.
This is a link for the instructions with pictures.