I am not sure that I understood the question well. Would that be correct:
I transfered from some exchange my funds to an address, which I imported as watch address on blockchain.info. Now I see funds but I can not spend it, what should I do?
If that questions is the same what is asked and user reports that blockchain.info has not helped at all, then I would assume that blockchain.info is not the owner of the address that was imported. Here is what you could do:
- To which address did you send your funds? If it is address that you somehow created with some application like bitcoin core, multibit, .... , then their application/user data folder must be still present on your pc (even if you uninstalled it). If that is the case and a wallet address you sent funds too is in ie. bitcoin core, you can export your private key if you write in the console
- If you imported exchange's wallet address, then funds would be still visible on exchange. In that case exchange would still have your coins and could help you
- If this address has never belonged to you, then you do not have the private key and you can not do anything beside to contact the owner of the address.
- Bruteforce is not really a option, but in theory it is possible. However, this is a point that you actually should forget.
I hope it helps. I see here only 3 possibilities, address belongs to you (you can retrieve your funds), address belongs to exchange (you still could get your funds) and that it belongs to somebody you do not know and you have no private key (in that case you can not do anything to get your funds back), maybe you could ask on internet who is the owner but I doubt any repl will come.