I was able to get the values, but the way it was done is not preferred. I don't want to have to pick apart my document to get the values I need. There should be (and probably is) a way to return a JSON object, or at least some sort of structured data.
var row = $('.selector').igGrid('rowById', ui.rowID)[0];
var dataID = row.getAttribute('data-id');
var cellValue = $('.selector_table tr[data-id="'+dataID+'"] td[aria-describedby="selector_table_ColumnTitle"]').text();
P.s. the code editor on here is awful. The cursor does not insert or delete characters at the position clicked and shown….