APA Style (7th ed.)
Since your instructor's comments aren't recoverable, please cite them as personal communication within the text e.g., (A. Surname, personal communication, September 4, 2018). See #9 in the APA Style (7th Ed.) Citations Checklist for information and examples, and note that personal communication is not included in a reference list because the information isn't publicly accessible (American Psychological Association, 2020, p. 260).
Reference
American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000
