After looking through the source I figured out the problem. Since I was using a custom function to fetch and add the data to the grid instead of using the grid's built in ajax functionality the loading text was not displaying. I ended up creating two methods, which I call when I start my ajax request and when it returnsm that do the same thing the built in ajax functionality does to show and hide the loading text. Here they are for anyone else who might be in the same boat.
function beginGridRequest(gridName) {
