I fell into his tricks AGAIN and hate myself for it

Background: he discarded me 6 months ago, wanted to continue as fwb, monkey branched into a rebound quicky while still sleeping with me. I went low-contact (only necessary work things) 2 months ago.

We work together, so we see each other almost daily. I have recebtly arranged my work schedule so that I see him as little as possible. Eat lunch when he doesn't so he can't join me. Have not talked to him about non-work things for two months.

This week he suddenly started to be SO nice to me. Got through all the walls I had put up. He has been at my desk multiple times a day, talking about everything and anything. Invited me to lunch and picked a table away from everyone else to eat alone with me, even though there were collagues around. Stared into my eyes for like 10 seconds without breaking eye contact - and even then I was the one to look away.

We had Christmas party at work yesterday. He had suggested we could take the same bus away from it afterwards, since we go to the same direction. He was normal during the party, talked to me a few times, joked even.

15 minutes before the bus left, I was looking for him and could not find him. I missed the bus while looking for him. The last bus of the night.

I texted him, "where are you", and he did not reply.

I had to stand outside in the cold and wait for an Uber for 45 minutes because of this.

I still don't know where he went. Just disappeared. I even asked a collague, and she said she had been talking to him but he had apparently just suddenly disappeared without saying anything to anyone.

I am SO mad at myself for missing that bus because I was so worried that HE might miss it and be left alone, drunk, in the cold, hurt himself, whatever. While he apparently does not even care if I fucking died because it is already afternoon next day and he has not even bothered to reply to that message to ask me if I am even alive.