If you read the context, it's quite clear that he's only referencing his own bitcoins.

    [12:02] <JonWickedFire> How much did you lose yourself?
    [12:04] <MagicalTux> Well, technically speaking it's not "lost" just yet, just temporarily unavailable
    [12:05] <JonWickedFire> Well, how much is unavail for you?
    [12:06] <MagicalTux> I'm not even sure
    [12:06] <MagicalTux> didn't check my wallet before pushing the site offline

That final line makes it very clear that he meant he didn't know how many BTC he had in MtGox and thus "lost". How you clipped it, it makes it sound like he might mean he doesn't know how many are temporarily unavailable on mtgox as a whole.