The e-mail from David's may have implied that the 70% would be refunded to the renter (it's understandable that this would be a more favorable impression to leave the owner with) but, as others have reported, it's more likely that the renter actually still received a voucher "funded" by the money that was returned.
But those funds almost certainly won't be tucked away in escrow waiting on the renter to redeem their voucher. On the contrary, the funds will be used to cover immediate costs and, hopefully, funding will still be available when renters attempt to make new reservations with their vouchers.