Hi @Angela C,
Google or the user are the only ones that could remove them and Google does removes or filters reviews for a wide variety of reasons.
Did either or both of them post their reviews while at the practice by chance?
If not, then a link to your listing would be helpful so we can take a peek. We can sometimes still see the reviews from our end and if so, we may be able to give you a good idea about what happened or suggestions about what to avoid in the future.