Correcting Overset Text
What is overset text?
Overset text will vanish from your content if it can't fit into a certain text frame. InDesign doesn't delete the text, but it isn't visible.
A clear sign of overset text is when the text frame shows a red + plus sign in the bottom right.

What to do about it?
If there is space on the page (as in the example below), click on the text frame with the direct selection tool (black arrow). Then select one of the white boxes on the frame's edge and drag it to enlarge the text frame.
Do not resize the frame beyond the page's margins or make the text frame wider than four columns.
To fix overset text manually
Click on the red box in the lower right of the text frame. Your cursor will turn into a loaded place gun. Then draw a new frame where you want it.