This is what the1203.4 section states
Dismissal of an accusation or information pursuant to this section does not permit a person to own, possess, or have in his or her custody or control any firearm or prevent his or her conviction under Section 12021.
And there are exceptions to when your prints will not show up even with an expungement -
1) When you apply for a for peace officer or public office,
2) In an application for a state license; or
3) Contracting with the California Lottery Commission.
In all other cases, you can deny the conviction.
Someone should have explained this to you - also keep in mind that when a check is run - an expungement will show as such - but no information is obtainable
If my answer has been helpful, please ACCEPT my answer so I get credit for my effort to help you . If I can be of further help, let me know. Appropriate FEEDBACK is appreciated as is a bonus. Thanks ~ Michelle