I dunno. I have an uncle that could disappear for a few months and nobody would be the wiser. Seems he does it with some frequency. It happens.
Having put in some time out in the wacky Pacific... I don't have a hard time believing this one. The Pacific is a really, really big crick. The parts that are outside of the usual routes for shipping traffic are big chunks of water. You could drift out there for a really long time and not see anybody.
I watched a box of water about halfway between San Diego and Honolulu for 30 days one time... and we didn't even see the other ships that were supposed to be in the neighborhood.