Try the following, make a selection of the textframe that has the table, it will search only on the first table of this textframe. You can change the value of the variable text to the value you want to search.
var text = "sample"
var tb = app.selection.tables
var firstRow = tb.rows.cells.everyItem().contents
for(var i = 0; i < firstRow.length; i++)
if(firstRow[i] == text)
This has not been tested in tables with merged cells etc, the code should give you idea enough to make the changes as needed by your workflow