Detecting when data drops off & moving rows to amother sheet

Hello everyone!

I'm attaching a spreadsheet I'm working with as a hobby right now. I will describe what I want to do with this data and I hope you can help me learn how to do it.

Essentially I want to find when a name in column C is removed from the data set. When a name is removed from column C, I want to take all of the corresponding data (columns A through D) for that data and add it to a new set.

Thank you!