I can see why you want the genuine answer to a genuine question.
But I would hang fire and resist the urge.
As you begin to heal from your, frankly utterly cruel, childhood trauma, you will find (speaking from experience here), that your need to do this gets less and less and can completely go.
If you get to that point (i hope you do) it is highly likely you will be glad that you didn't for the following reasons:
The people who were at that table with you were likely just small minded people mostly concerned with their own social status and were probably grouping around one mean person who was singling you out for petty dislike in a playground politics kind of way (very childish and pathetic, but not unusual).
They didn't then, so may well not now, have the emotional intelligence or compassion to see where you might be coming from, put themselves in your shoes, and answer honestly.
They may find it amusing that you're asking this question after all this time (over a decade), because it is very clear if someone comes back to something after a long time that it really bothered them. They may share this amusement another from that group (they may still be in touch).
If in their eyes it was no big deal, the fact you've held on to it all this time (very understandable from your point of view), could look to them like a 'massive over reaction'.
That's just one scenario.
But like other risky scenarios, you have to be ready for all the possible reactions.
It's a bit like getting in touch with your birth parents, you shouldn't do that if you're only imagining a joyful reunion and would be crushed by indifference or even anger....
Even if they don't find it funny (either strange or funny haha). It's unlikely they will actually be frank with you. You are an ex colleague from over a decade ago, it's more likely they will wonder why you've been following their insta all this time of you've been upset about this for an these years and say something like, 'oh we were young and foolish, it didn't mean anything, sorry if it upset you' <block on Instagram>.
The chances of them actually being compassionate and honest is the least likely outcome (though it is of course possible).
If I had to put money on this I'd say you were unlucky to find yourself amongst a group whose dynamic meant that the group culture wasn't inclusive and kind, but was still akin to the playground.
Young adults in their first big job, all carrying their own history of popularity (or not) and learnt experience of how you gain and hold popularity (can often be by putting others down).
Maybe ambition and wanting to impress, so vying to be top dog.
Maybe also insecure and not wanting to challenge someone who seems strong and has taken against you.
People who come out of a really tough upbringing (your parents said such hideous things! I'm so glad you're still here, that could easily not be the case, with such cruelty), often lack that ease of confidence that more fortunate people have, and people like this spot the weakness and exploit it for their own amusement / social status gains.
I'm 48 and I'm here to tell you that mid thirties is still early days for a full healing from this, it will get better and better if you keep seeking kindness, therapeutic experiences (either talking about your experiences with the right person, professional or friend - or things that make you feel good to be you, and do things that make you feel glad to be alive).
But I don't think these people are who you should go to for a release from this experience that haunts you.
It was a crucial time, of course it left a lasting impression.
But the release you want and need is better coming from this not mattering anymore, which I know is impossible hard to imagine right now, but actually will come and the day you realise you have it, you will feel lighter than you ever have before.
You will also be glad you didn't lose your dignity by getting in touch with this person.
Seek the release, but not in this very risky way, I think you are still too raw for you to weather it well if they don't react how you hope.