I don't know how good your polish is but it would be nice to have the help of some local polish members.
Melo already went way beyond as a non affected person.
Please FFS read the whole topic and not just the last 3 posts.
I will sum it up for you, although there are valuable and unfortunately a lot of simply useless informations to be found:
1. Their contract with the seller and you as a victim is unfortunately airtight, hiring a lawyer would be just wasted money(which you even cant since you are not the involved party).
2. Melo provided well researched links, use those instead of spamming a bank.
3. They state that you need to come to their branch(ofc unreasonable), therefore get yourself a person legally representing you, like a notary for example.
4. Sooner or later they must release the funds of customers that acted within the legal framework, its just the approach that makes the difference in the length.
5. If you want to go public with that case, there are links in the topic that would even consider such a petty case(try it on weekends).