I assume you're talking about Instawallet? Unfortunately, there is absolutely no way to recover bitcoins from just a Bitcoin address. Since all addresses used in Bitcoin transactions are public, if this
were possible than anyone could just take anyone else's bitcoins, and that wouldn't work at all. Instawallet is not going to be able to assist either, since they have no way of knowing whether you really are the owner of the account or just someone trying to steal the account owner's money. All Bitcoin transactions are irreversible and if you ever lose access to your account, the money is gone forever. Sorry.
Your friend's only hope is if the wallet identifier is in his browser history; if not, the money's gone and there's nothing anyone can do about it.
Warning
Please be very careful in using this site. The URL is the key to your Bitcoins. If you lose it, there is nothing we can do. In the past we have tried to help people, which have forgotten their URLs, whose computer or browser has crashed or who have copied the Bitcoin address instead of the URL. But we can no longer do that - the risk of us getting scammed by someone just pretending to be a forgetful user is too high. So again: The URL is the key to your Bitcoins. If you lose it, there is nothing we can do. No amount of extra information you provide, can prove that you are the real owner. It's all available in the blockchain for an imposter to access as well.
We would like to make this website safer to use, but we currently do not have time to do that. So we can either shut it down for the time being or put up a warning like this. We know that Instawallet is seen as a very useful tool by a number of my users, so we have decided to go with the latter option. Please consider yourself warned: If you lose the URL, your Bitcoins are lost, no matter the circumstances.
