In a lot of rooms, verbal is binding, but a number is usually accompanied by "raise" or forward movement of chips. In this instance, I don't think it's binding because the player doesn't have "thousand." It can't be binding if it's not possible.
Did the player do anything when he said "thousand"? Pick up chips, etc.
If this is binding and someone calls and player wins, is the person who called required to pay $1,000? If only