In quantum mechanics, an atomic orbital is a function describing the location and wave-like behavior of an electron in an atom. They are pen-and-paper concepts that we use to try to explain the arrangement of electrons in an atom around the nucleus. They don't really exist in real life, per se. So, whether the single electron in an orbital is ionized or not, it never exists. But the energy level represented by that orbital is always accessible to that atom, and if a proper amount of energy is supplied to the atom, the electron in a lower subshell will excite that previously empty subshell. Truly speaking, no orbitals, whether empty or containing electrons don't exist. However, when an orbital is empty, it does not exist anymore and does not have any influence on the behaviour of the atom, until it is filled again.
Proof of empty orbitals still existing (or can be made to contain to electrons again):
In Peter Atkins' Physical Chemistry, while talking about transitions, he says
The Lewis concept of a ‘lone pair’ of electrons is represented in molecular orbital theory by a pair of electrons in an orbital
confined largely to one atom and not appreciably involved in bond formation. One of these electrons may be excited into an empty π* orbital...
This is one of the many statements that give the proof of the existence of orbitals even if they are empty, though they do not truly affect the immediate existence and properties of the atom unless electron addition or excitation is being considered.