/lib/modules/2.6.22-15-generic/modules.dep mysteriously disappears

[Matthew Flaschen]

The file /lib/modules/2.6.22-15-generic/modules.dep mysteriously went
missing from my machine.  Either it never got installed or it somehow
got deleted.  The way I discovered this is that running:

cryptsetup luksOpen
/dev/disk/by-uuid/2e084ab9-0df7-4f6a-bb92-0a596492b4f0 encThumb

(actually in a script, but I tested afterwards again just this line)

failed for the first time with a new error:

Failed to setup dm-crypt key mapping

similar to the one described at
https://bugs.launchpad.net/ubuntu/+source/cryptsetup/+bug/132373

(though I think the cause is unrelated).

Needless to say, losing the encrypted data would not be a fun time.
Anyway, I ran:

modprobe -l *cryptsetup*

and got an error that /lib/modules/2.6.22-15-generic/modules.dep was not
installed.

Reinstalling

linux-image-2.6.22-15-generic fixed the original problem and the error
with modprobe (note as I discovered the actual module is dm-crypt, but
modprobe -l should never give an error for a bad module; it just doesn't
print anything).

So my question is, what could have caused this file to go missing, and
should I be concerned?

Matthew Flaschen