Cannot mount encrypted home after password change, ecryptfs not configured (no passphrase set)

Cannot mount encrypted home after password change, ecryptfs not configured
(no passphrase set)

I recently forgot my user password from a relatively fresh Ubuntu 13.04
installation (dual-boot with Windows 7, latter more heavily used). During
setup, I had selected the encrypted home directory option but
unfortunately skipped the step asking me to record a passphrase.
I managed to set a new password for my account by booting into single-user
mode, but as described in "can't login after password change (ecryptfs)",
I am thrown back to the login manager when trying to use my new password.
The answer to aforesaid question linked me to Annoyance changing password
with Ecryptfs, which suggests running ecryptfs-mount-private, but
unfortunately that merely returns ERROR: Encrypted private directory is
not set up properly.
Does Ecryptfs set a default passphrase in such instances, or if not, is
there any other way to recover my data? (Said data largely consists of a
few saved image files and Oolite savestates, so I wouldn't mind a total
loss that much … but it's the principle that matters here.) If not, would
the easiest way to get a usable system again be a partition wipe and
reinstall? (In this case I would probably want to delete the single
partition set by Ubuntu setup and define multiple partitions myself ¯
advice on what amount of swap space is recommended on a 64Bit system with
8GB RAM would be welcome.)