Oh, yep, fledgeling baby tree-birds have more volume than sense. I've moved jay fledgies away from the road and had them demand food the entire time I was carrying them. Atricial birds (the ones that are naked and helpless as babies) only learn to be birds after they jump out of the nest and walk around on the ground for awhile, unlike precocial chicks (mobile at birth, think chickens) that start learning right at hatch, so they aren't terribly smart when they hit the ground for the first time.
Probably the sparrow baby thought they were the same species!
That's really cute! Take a picture if it happens again. A minute or two longer of contact won't hurt anything.