If this was some romantic interest of yours, I would highly recommend you spare them your "feelings" and unnecessary melodrama of rehashing the past, unless it's your position (being single) and your intent to actually act upon said feelings (sex). Otherwise they may interpret your intentions to be nothing more than you just looking for a boost to your self-esteem and ego.

I think if you want to contact them, you should. The only time you shouldn't is if they have told you "please don't ever contact me". Then you should respect that. No one that wants nothing to do with you wants to hear from you.

But if they don't respond, that's your answer.

if they do respond, realize they might just be being nice, and take the response as just that.

FFS can't you write an email!!?

I tried contacting a former supervisor from a job I worked four years ago. She and I both couldn't stand each other and we didn't work well together at all. Her humour didn't mesh with mine and she was one of the reasons why I quit. Years went by and then we ran into each other on the bus. We talked things over and it seemed like things were patched up. But then when I messaged her on Facebook, she totally and completely ignored me. I contacted her because I wanted to reconnect. Maybe take her out for a coffee or something. I eventually gave up and learned to accept that we were never meant to be friends. Sometimes more often than not, no message is a message. So if you're fifty fifty about contacting your former coworker, then it sounds like you've answered your own question.