B.S.
Is he able to nap okay at daycare while you're at work? Maybe his afternoon nap isn't going that great and therefore he's overly tired when you pick him up. Or is he eating okay at daycare? If not he could be hungry earlier than his regular dinnertime. I've always found that when my kids miss naps or wait too long to eat they get very cranky. The other mom was right about the whole communication thing too, your son is the age where he may be trying to communicate with you but is unable to yet.
I'd try coming home, fixing a small snack and drink (nothing to spoil dinner of course) and cuddling up with him on the couch for a few minutes so he can relax and unwind with you while he eats his snack. You can talk to him, ask how his day was, tell him how much you missed him (of course this will be a one-sided conversation!) but it might set him at ease to hear your calm voice and feel your hugs.
Good luck!