OP Here. So he left, it was all fine, but a bit flat! I worried about nothing but it feels a bit weird. Oh well.
Our boss had suggested to leaving coworker that she would take him for coffee to do a handover and this was agreed a few days ago, and yesterday she mentioned to me she was making cupcakes as well.
However she isn't known for her time management or organisational skills so when it got to after 3pm and we hadn't even seen her today, coworker and I weren't surprised. She eventually came in and said ' hi, sorry I'm a bit behind, can I take a look at project B with you quickly, oh and here's some cake'. So we all three looked over the project and she had to rush to another meeting she had scheduled in earlier that day, so she has asked coworker to drop by later in the week to discuss handover and future freelance work.
It got to 5.30pm, when we officially finish, and coworker was getting a lift home from a friend who works nearby and had to go. He went to say goodbye to our boss only to find she'd left for the day without saying anything!
So we exchanged brief pleasantries in what felt, to me at least, a slightly awkward way, and he said ' see ya soon' and that was it.
Hey ho, not worth the worry!