Script to loop through a Google sheet and set returned data as a note on a selected cell.

showDates.gs

// Globals yada yada
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
var ui = SpreadsheetApp.getUi();

// Once all is said and done, add the info to the selected cell
function addNote(e) {
  var cell = sheet.getActiveCell();
  cell.setNote(e);
}

// Loop through the dates to find the ID match
function findDates() {
  // The selected ID...
  var idToMatch = sheet.getActiveCell().getValue();
  
  // Get all the data from the lookup sheet
  var range = ss.getSheetByName("raw").getDataRange();
  var ids = range.getValues();
  
  // Use the Logger for debugging. It'll make you feel better.
  Logger.log(idToMatch);
  
  // Initialize an empty array to hold returned dates from the loop.
  var dates = [];
  
  for(var i=0;i<ids.length;i++) {
    
    // If the ID in the range matches your selected ID, push it into the array
    if(ids[i][1] == idToMatch) {
      var date = dates.push(" " + Utilities.formatDate(ids[i][0], "EST", "MM-dd-yy"));
    }
  }
  
  // Send the array with dates to add the note to the cell
  addNote(dates);
}

// Menus and interaction stuff
function onOpen() {
    ui.createMenu("Get Dates")
    .addItem("Run","findDates")
    .addSeparator()
    .addItem("Help","helpText")
    .addToUi();
}

// Make the help text actually readable when you need help.
function helpText() {
  var htmlOutput = HtmlService
  .createHtmlOutput('<p style="font-family:sans-serif">Highlight a student\'s ID and select <b>Run</b> from the <b>Get Dates</b> menu above. The dates a student is logged will be added as a note to the cell.</p><br /><p style="font-family:sans-serif">Look at the dates by hovering over the cell with the note.</p>')
    .setWidth(250)
    .setHeight(300);
  ui.showModalDialog(htmlOutput, 'Help');
}