Can a Familiar holding an item take it into the pocket dimension when dismissed?

I had a weird thought related to the Portable Hole & familiars. If a familiar is holding a portable hole, and you dismiss it into it’s pocket dimension, what happens?

Does the portable hole do it’s Astral Plane vacuum thing, the familiar’s dimension isn’t from an item? I would think not because it doesn’t seem like that would happen with a Bag of Holding or Portable Hole and say the Rope Trick or Demiplane spells.

What happens if you get in the Portable Hole, have the familiar take it and disappear into the pocket dimension? Are you permanently stuck with out something like Plane Shift? You could conceivable get out of the Hole into the Pocket dimension, but there doesn’t really seem to be any way out because you can’t resummon the familiar outside either the pocket dimension or Hole. Can you toss an enemy in the Hole, have the Familiar take it into the pocket dimension, the enemy could get out or break out, and conceivable the familiar could take the hole and be resummoned, leaving the enemy behind. Is that enemy then permanently gone unless they have Plane Shift if you permanently dismiss the Familiar before creating a brand new one?