jQuery Grid Plugin - jqGrid

I've been banging my head for a little while watching a weird jqgrid behavior and trying to get around it. I'm using v.3.7.2. (though this issue also occurred with v.3.6.5). Here's the problem. I'm using a grid with these grid settings (i skipped some irrelevant params):

-------

var gridOption = {

 rowNum: 10,
 pager: '#pagerId',
rowList:[10,20,30],
 
 ....

datatype: 'local',
};

To bind my data to the grid I execute these commands:

this.jqGrid.setGridParam({ data: rows });

this.jqGrid.trigger('reloadGrid');

The rows object has a bunch of data for the grid retrieved from the server. Each row has an object with Id property holding a unique record Id in my db. After binding the data and before invoking 'reloadGrid' the jqgrid.getDataIDs() method returns an array with IDs exactly matching those stored in the rows object. Then after reloading the grid this method now returns me an array of values starting from 1, 2... So it looks like the initial IDs are gone and the new IDs are generated after reloading.

What the heck am I doing wrong there?:)