Jessica...
if the circled icon (and others within the table) is the one they are clicking on... the warning pops up...
I am assuming you are using a current version of PRO.
If you have seen such behaviour, then you could report first a first hand experience, and it would lend some credence to the claim.
However, as with many errors of a 'just happened' nature, further inspection usually reveals that the user clicked a button on a dialog (like the one I posted) hoping the things will be better... ( I teach and this at least has been my observation )
Try as I could, I was unable to replicate an unintentional field deletion that didn't provide an error warning.