Find Controls nested inside Repeater Control

I’m trying to find the values of TextBoxes which are rendered in a Repeater though a UserControl, i.e. the Repeater has a Placeholder for the UserControl, and inside the UserControl is where the TextBox markup actually exists. I’ve done this before with TextBoxes directly inside of a Repeater before, which was fairly straight forward, and I’m wondering why this apparently can’t be accomplished the same way. Here is the Default page with the Repeater, which contains a Placeholder…