(CNN) An Iowa grandmother won half the $687 million Powerball prize and she didn't even know it at first.

Lerynne West , 51, bought her tickets at Casey's General Store in the small town of Redfield, Iowa, while grabbing pizza and coffee with her sister. She said it was a special day because she had bought her first home and was moving in that day.

West thought she put the lottery ticket in her purse, but she accidentally left it on the floor of her sister's truck. It lay there for a couple days.

When a friend texted the day after the drawing to ask if she had won, West said she hadn't had a chance to check. She rifled through her purse and realized she didn't have the ticket. She quickly called her sister, who found it.

West looked at the photo of the ticket her sister sent her and checked the numbers on the lottery's website -- she had won!

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