I guess if you take it literally then you have won a weekend for 2 in Poland, it just did not include the means to get there.
If they had said "All inclusive weekend for 2 in Poland" then I guess you would have had cause for complaint.
This, of course, is where the flexible use of language comes into play in the world of marketing.
So for example "Strawberry yoghurt" must have some strawberry in it, but "Strawberry flavored yoghurt" does not need to have ANY strawberry in it, just Strawberry flavoring, which can be artificial.
I know that is nothing to do with holidays, but it is just to make the point that "a weekend for 2 in Poland" can mean different things to different people.
It is like people who come on here and say "I have been rung up and told I have won a free holiday". Often this is a scam and it turns out this "free" holiday can cost you hundreds of pounds.
I guess there is not much you can do about it now.