With the Career Planning form on file, just advise the graduate school of the situation and ask if you can have your file sent from the Career Planning Office. You may also want to add someone in higher authority at your place of employment. Some large corporations will not give written references . In that case, see if your supervisor will agree to be a telephone reference for you. My supervisor, Ms. Joan Jones, has agreed to be telephoned as a reference.
Experience is experience , whether it was paid or volunteer.
Treat volunteer work as a job for reference purposes.