I made a mistake by looking away when he looked at me that he looked disappointed
OK, first I'm going to write something for the sake of all the women out there dealing with Polish men.
It took me a while to realise this, but where I live men are doing something that I'd call "testing the waters". I don't know whether it's "a typical trait of Polish guys", I've never lived abroad, so I can't say, but I think it's possible that Polish men are less bold than men in some other countries. So, they often don't hit on you right away, first they try to make an eye contact to check if you're interested (I'm mainly talking about everyday situations - at work, at the store, at the doctor's, etc.). If you look away looking indifferent they interpret it as lack of interest and they can get sad, offended or angry even. It's sometimes small things that can put them off and you may get surprised how petty and vindictive men can get, so it's better to be careful, especially with co-workers who are higher on the hierarchy ladder at work.
And now I'm going to write something for the sake of Polish men out there.
If a woman doesn't seem to reciprocate your interest when you're giving her "the look", don't take it so personally. Do you know how many such looks women get? A lot. I'm guessing that the more attractive the woman is the more such looks she gets. We can't possibly date or get interested with every random guy that looks at us in the street, at work, at the store, at the dentist, etc. We don't smile not because we're b1tches or think we're too good for you, but because we don't want to encourage you to hit on us and get rejected and get hurt as result. Also, women have boyfriends, partners. The fact that she isn't wearing a ring doesn't mean that she's necessarily single. So, again, don't take it personally.
One guy in particular got stuck in my head. I was waiting for a visit at the dentist. He went out of the dentist's office, saw me and his face was immediately like "OMG, A WOMAN!" lol So I assumed my poker/indifferent b1tch face and pretended that I went back to my nap. He started to put his clothes on and when I looked at him again he looked like a puppy who got kicked in the stomach. He looked so sad, like he was thinking "I'm not going to get a woman ever in my life". I really felt sorry for him, I felt like hugging him almost and saying that he'll find someone for himself :/ Because of such reactions (and the angry, entitled ones) I get somewhat tense if there are men in a waiting room at the doctor's or other such places where you have no other choice but to look at other people. I don't want to hurt or offend anyone so I often pretend that I'm taking a nap or letting my eyes rest (my usual strategy lol).
There's another thing. Women can be shy too. And they often have a lot of complexes concerning their looks, especially Polish women apparently. We aren't telepaths so more than just one look may be needed to make us realise that you're interested. Don't give up so easily, guys.
How can I find him
Ask people at work who know him what happened to him and whether they can help you to contact him.