Following up: In the end, I am using conditional formatting on the spreadsheet to make it obvious which cells on the spreadsheet have formulas. Then, if another user inserts some columns without copying the formulas, I see a hole where the formulas should have been.
I have to enable macros and then create a function inside a "Module" like this:
Function IsFormula(Check_Cell As Range)
IsFormula = Check_Cell.HasFormula
End Function
Then conditional-format the cells so that if =IsFormula(XX) returns True, then shade the cell light gray.