What happens to things that fall into black holes? Here is an admittedly highly speculative head-twisting suggestion published by National Geographic. It offers an explanation “certain features of our universe deviate from what theory predicts, according to physicists.”
I see that Science has reported on the same theory by the same scientist (BTW, his name is Nikodem Poplawski, and he works at Indiana University in Bloomington).
A long time ago, in a universe much larger than our own, a giant star collapsed. Its implosion crammed so much mass and energy together that it created a wormhole to another universe. And inside this wormhole, our own universe was born. It may seem fantastic, but a theoretical physicist claims that such a scenario could help answer some of the most perplexing questions in cosmology.
Near as I can tell, yet another untestable hypothesis, along with the Local Pockets model wherein we are in a relatively small area of expansion between areas of compression, and String Theory that postulates many dimensions that are just too small to see (below the Planck limit).
Unknowable, unprovable, unbelievable…
but it does make a nice premise for some speculative fiction!
BTW, I think I saw an episode of "Star Trek: Voyager" where someone was trapped in a bubble universe.