Can you tell if someone's dating based on their WhatsApp activity?

I like I guy at work, I'm not sure whether it's slightly reciprocated or not because it's fairly new. We exchange some jokes and words when we see each other, I noticed the more I like him and the more I get touchy when we laugh. Our banters are pleasant, he's engaging and laughs at my jokes but could simply be friendly and polite. Not sure whether he understood something or not. He's the most reserved person I know, never asks personal questions, keeps it professional etc.

Anyways, while we were working on a project I saw his phone screen lit up, didn't look at the names also because I can't see really good without glasses but I'm sure I saw some hearts twice. He also wears a hair tie around his wrist.

I started to check his WhatsApp status a while ago and noticed he was online at 3 AM and also at 6 AM and my gut feeling is telling me he's taken.