No, this is a long-standing myth which is entirely false. It wouldn't make sense from an engineering standpoint as it would move the pressure differential to the flat (and thus weak) floor of the airplane, rather than the round (and thus strong) outer hull.

However, the hold is not climate controlled to the same degree as the cabin, so he may have gotten cold-ish. But even then, the cargo hold is not a particularly inhospitable place. Living things (animals) are for better or for worse shipped that way all the time.