Boiler maintenance

Hi. I'm just leaving my house and got a guy out to do the boiler service, which he wouldn't do because there is a leak in the boiler. The heating works fine so we didn't notice until then. We had a check done last year, when it was fine, but I have lost the attestation and the guy's contact details (I think he has gone back to Poland). Does this make me liable for any damage? I'm Worried they might take liberties with regards to necessary work if I can't find the attestation. Not really sure what to do. Could ask a heating engineer to provide an attestation upon receipt of payment but that would be immoral I feel. I know it's my fault for losing the thing.