if my theory is correct, (well, not MY theory, but the theory I choose to pass along), the main bulb is down there a little lower than the rest of the smaller ones. they tend to sink a bit as the roots pull them deeper and deeper into the soil. also, if my theory is correct, the main bulb will be a lot bigger than it was when it was planted, and it will be obvious that it needs to be divided. if you so choose that is. should be quite easy to locate. like I said, some of ours that have been in the ground for several years have grown to be the size of grapefruits, with two or more MAIN stems coming from each bulb. these little buls will take a few years to mature so don't expect many flowers from them just yet. we always pluck them off and replant them in a new location for them to grow a season or two. I would wait until late fall to dig them up however. you don't want to disturb them during the height of the growing season by digging them up now.
