Hi Gretchen, Her burial place might be included in her obituary. You can request her obituary from a volunteer at freepages.genealogy.rootsweb.ancestry.com/~obitl/volca.html Scroll down to San Diego Co. and choose Peter.
If that doesn't work out, contact the San Diego County Library at sdcl.org Hover over Community Services Click on Libraries Click on AskALibrarian on right-hand side and ask for a copy of her obituary.
If one wasn't published, her death certificate should show where she was buried. You can request a copy of her information death certificate from the San Diego County Recorder's Office, http://arcc.co.san-diego.ca.us/services/birthdeath_certificates.aspxhttp://arcc.co.san-diego.ca.us/services/birthdeath_certificates.aspx . They do charge a fee.
Is it possible she's buried next to her husband Chester but the family didn't have the money to engrave her death date? Maybe a family member picked up her cremains and didn't bury them? Successful Searching!