... I lost 1 mBTC once and was able to bruteforce it back because it was located on an address which was constructed by an algorithm.
It's comparable with HD wallets which generates all future addresses based on a seed. As long as you know the seed you are able to recover all the coins.
How do you brute force your coins back?
It's impossible to brute force private keys of course but If you got the wallet.dat and you have an idea about your password then It could be possible to crack using some tools. See here