Sent 20BTC by mistake?! Thats the biggest mistake i'll nvr forget.
This is hardly believeable. OP knows about blockchain.info and has 20 BTC or more but doesn't know that bitcoin transactions aren't reversible? From the FAQ on blockchain.info:
https://blockchain.info/wallet/bitcoin-faqWhat is a Bitcoin address?
A Bitcoin address is a unique identifier which allows you to receive Bitcoins. With PayPal you send funds to an email address, and similarly with Bitcoin you send funds to a Bitcoin address. For example, this is one of our Bitcoin addresses: 1JArS6jzE3AJ9sZ3aFij1BmTcpFGgN86hA
Please verify that you have copied the destination address exactly before sending Bitcoins to it. Bitcoin transactions are not reversible!