CDC’s General Best Practice Guidelines for Immunization states that, in general, you should only accept written records as proof of vaccination. If the person’s recollection is wrong, and the person is susceptible, then not vaccinating leaves them at ongoing risk.
If you have no record of HepB vaccination and you intend to do the triple panel screen, it is reasonable to proceed with giving the first dose of HepB vaccine after drawing blood for screening. If that triple panel screening test shows evidence that further vaccination is not needed, or if the patient locates records later, then discontinue vaccination at that point. If screening is not done, and records are unavailable, complete the series. If you screen the patient after a partial HepB vaccination series, the screening results might show a positive anti-HBs antibody; however, you should complete the vaccine series to ensure the patient develops the intended long-term protection from infection.