The Lovey Boat

When our son was about 2 weeks old, he managed to get his thumb in his mouth, though it didn't look very comfortable since all of his fingers were plastered on the rest of his face (picture an octopus attacking). Impressive as it was, he lost it as quickly as he found it. Several weeks later (over a month, IIRC), he slowly began to realize he had control over the hands that seemed to keep attacking him. He found the thumb, and it's been a constant source of comfort ever since. When he's tired, the thumb goes into the mouth, and he'll gaze around until he falls asleep.

A Baby Center e-mail today said the following:

"Chances are good that your baby's grown attached to a certain blanket or toy. Transitional objects may help your baby weather potentially stressful experiences — such as a doctor's visit or a trip — more easily. You may want to buy a duplicate of her lovey (or cut the original in half, if it's something like a blanket), in case you need to replace a lost one or take it away to clean it."

So here's my question:
If his thumb is the only external source of comfort besides dada and mama, is his thumb his lovey or is he lovey-less?