So you're having a problem with hiding columns, or actually unhiding. Basically, there's only a couple ways to find out if someone has hidden a column. You'll see at the very top, A, not B, but you'll see C. So you'll see that there's two columns here, but these are not lined up. They're supposed to be A, B, and C. The second way you can find out if someone has hidden a column is you'll see these two little black arrows. And when you highlight over them, you move your cursor over them, you'll, they'll be clickable. And this is how you unhide a column. You just click on that arrow. If you noticed, however, when it's hidden right in the middle, It is the line that you can move to increase the width of the cell or the column.

So you do have to actually click right on the exact arrow. You can click on either the left one or the right one. It will unhide the column. If you're looking to get more out of your Google Sheets than you ever have before, consider subscribing here on YouTube to Better Sheets. I go way deep into getting more out of your Google Sheets, like automations and formulas and formula combinations that are going to help your work so much more.