Were you actually in work in the weeks leading up to it or had you been off sick?
It's usual for people to just "drift away" if they're not present in the workplace, shouldn't be like that, but it's harder to mark the occasion if you're not there and maybe havn't been in much contact leading up to it.
Similar happened to me, not from retirement, but from leaving one firm to join one of their clients. I'd already been spending ever increasing amounts of time on the client, plenty of days working at their premises and even in our own office, I'd spend most of my time working on the client, so wasn't really working on jobs with other staff. By the time I was offered a full time job there, I was probably working there 4 days out of 5 anyway, and in the week or two before "leaving", I was there all the time. "Leaving" day came and went, and there was nothing to mark the occasion because I wasn't in the office. Felt sad for a short time, but in reality, I wasn't there, so what did I expect? Certainly didn't expect them to come and see me in my new workplace. It was just a big "non event" for all concerned. Obviously, I soon got over it because I was busy with the new job, but I can see it would leave a void for someone retiring.
Similar happened again a few years later in a different job, I'd been having problems with the bosses, and we mutually agreed that an instant termination would be best all round at a meeting one morning. I "left" that lunchtime, the condition being that I'd not tell the other staff and just go, which I did, felt really strange appearing to go for my lunch but knowing I'd not be back. Bosses didn't even tell people en masse either, so the other staff just thought it strange I'd not come back, and it was a few days apparently before the staff grape vine informed them all I'd gone and wouldn't be back. So again, no actual "marking of the occasion". That time, I'd set up my own small business, so was busy with that, rather than dwelling on lack of a leaving do.