Hmm, well, they would have everything they need to locate it, if you gave them that address (probably available in bitfloor account history), your password, and the approximate time you created the wallet (probably a few minutes before the transaction timestamp.)  That's not safe for you (though what choice do you have at this point?), and not safe for their users, but perhaps you can give them enough evidence to convince them you're really the owner.  I'm thinking of a scenario where someone finds: "blockchain.info wallet password: abc123" on a post-it note but no wallet ID or alias.  This is already a disaster for the wallet owner, but it also seems like blockchain.info should try to not help thieves find the last bit of information they need to steal coins.  No accusations of you, just thinking from a wallet host's perspective and their responsibilities.  Best of luck.