The meaning of "expungement" can vary from state to state. You are correct that a "true" expungement would delete all the records. Many state licensing boards, for example, still want you to let them know about expunged records. There may be another way for them to "see" the records.
In California, for example, there is not true expungement. it is dismissed and it should show that under a finger print check as being dismissed. I can't tell you what happens in other states. I'm sure it depends. Sometimes when records are supposed to be deleted, there are errors, and it doesn't happen correctly. So, I think the best way to know is to do a self check and find out what is or isn't on your record.