Which dice site do you deposit your .4btc? There are many dice site out there and mentioning one which has been closed will help the community identify it for further investigation.
He did mention the site name already but it can be confusing for other who have never heard about satoshidice as he write it separately "satoshi dice".
The only way to get his money back is by contacting the support, although satoshidice is a DAPP site now but if there is no ownership changing since the date OP sent the bitcoin then there should be still a way to get the money back.