Find Font used in Numbers
To check which cells have the font family "TIMES-Roman," run the following script. It will generate a dialog that will display the column and row of any cells that contain that font. To run the script:


Open your spreadsheet in Numbers and close all other open spreadsheets
Open Script Editor (/Applications/Utilities/Script Editor.app)
Switch the language in the top left corner of the window from "AppleScript" to "JavaScript"
Paste in the script below and click the button with a "play" icon at the top of the window


If you see a blank dialog box, the script couldn't find any cells with the offending font. Please also note that this script assumes that you only have one table and one sheet in your document.



var offendingFont = "TIMES-Roman"

var culprits = []
var table = Application('Numbers').documents[0].sheets[0].tables[0]
var cols = []
for (var i = 0; i &lt; table.columnCount(); ++i) cols.push(String.fromCharCode(65 + i))
var rows = []
for (var i = 0; i &lt; table.rowCount(); ++i) rows.push(i + 1)
for (var r of rows) {
    for (var c of cols) {
        if (table.cells[c + r].fontName() === offendingFont) culprits.push(c + r)
    }
}

var app = Application.currentApplication()
app.includeStandardAdditions = true
app.displayDialog(culprits.join(", "))


Since you said you never use any flavor of "Times" font, here's an additional, altered version of the script that finds any font with "times" anywhere in the name (this might produce better results):

var offendingFontExcerpt = "times"

var culprits = []
var table = Application('Numbers').documents[0].sheets[0].tables[0]
var cols = []
for (var i = 0; i &lt; table.columnCount(); ++i) cols.push(String.fromCharCode(65 + i))
var rows = []
for (var i = 0; i &lt; table.rowCount(); ++i) rows.push(i + 1)
for (var r of rows) {
    for (var c of cols) {
        if (table.cells[c + r].fontName().toLowerCase().indexOf(offendingFontExcerpt) &gt; -1) culprits.push(c + r)
    }
}

var app = Application.currentApplication()
app.includeStandardAdditions = true
app.displayDialog(culprits.join(", "))