Error message font

Question

In opening Numbers 3.1 documents on my iPad, I keep receiving the annoying error message that I'm missing a font. Okay, easy enough, I thought...I edited the document (on my iMac, also using the most recent Numbers) by selecting all its text, and changed the font to one that's available.
Except that, apparently, the unavailable font (in this case, Univers), appears to be hidden somewhere else in the document. I am baffled as to how to get rid of this annoying error message, which comes up every time I open the document on my iPad - a waste of time.
Where might this reference to needing Univers exist in my document, and how can I get rid of it?

Answer 1

I think I've figured it out.
On my iPad, I clicked on an empty cell. I then chose "select all" (if that option doesn't show, the cell is not actually "empty"). Then, using the formatting "brush," I click on "Table Options," and then "Table Font," selecting a font that's on the iOS version of Numbers.
That seems to work. Selecting a cell with content, then expanding the selection borders until the whole spreadsheet is selected, for some reason does not work - apparently that handles only the fonts in the cells...leaving this wondrous "table font" untouched.