The object of Filevault is so that no access is possible via any other means except the secure path laid out with a fully running OS X to ensure your data is secure. This is a very secure and limited access state intentional to supply the security provided.
The Lion Recovery Partition is just a tiny program on a partition, the window asking for your password shouldn't have appeared at all.
If the Lion Recovery Partition allowed a unlocking of a Filevault drive, means that that code could be easily cloned, altered and used to crack any Mac with Filevault with a simple USB key. The government snoops would be screaming if they knew this was possible.
Filevault is a complete waste of time and effort for most users, it hogs CPU cycles, slows down one's machine and disables recovery options if OS X fails to boot as one can't decrypt the image and simply recover files using a alternative means (like Firewire Target Disk Mode for instance)
It's better for most users to leave Filevault alone and either use a Iron Key or individual file/folder encryption software on just the items they need.
This way if something goes wrong, the files are either off the machine or the drive can be accessed and the encrypted files/folders transferred to another Mac, decryption software installed and the correct password used to decrypt the files.
Military and Government parnoid level total drive encryption is overkill for most regular users needs as they don't access super secure networks that require it. And since most all of those super secure networks are not on the internet, makes it inaccessible to most users anyway.
Most users just need a folder or two encrypted, with the ability to move them to another comptuer, not their entire drives encrypted in a unmovable state.
Also the advatage of having something like a Iron Key is that one has the files off their computer and can easily and quickly dispose of the Iron Key in a rapid manner smashing it with a hard large rock for instance and spreading the pieces around at random, or burying it in the ground for another, try doing that with a computer. 😝
As if you don't already know, Apple is vulnerable to government influence, they certainly have complete access to Filevault no matter what Apple says.
A four character password?, heck I could crack that on my Mac in about 5 minutes.
So if your not super serious about protecting your data, just want to keep snoops at pay, do the file/folder encryption or Iron Key method instead of Filevault, don't be sorry later like your sorry now that you can't repair your drive permissions or access your drive if OS X fails to boot.
