If the BCH is escrowed on the blockchain, where is the fiat escrowed?
So the FIAT didn't go into escrow. It went straight to the seller who then releases the BCH from escrow. If the seller does not release it then you can initiate a dispute.
The seller presses a button to release the BCH from escrow. Not all sellers ask for cell phone verification. Mine didn't and I will never choose one that does.