Normally when you do a medical the AME records hours since last medical, also at LPC the log book should have been endorsed by the TRE, and if all else fails the flight time records by tail number can be crossed checked. If the company went bust there is still a legal obligation to retain crew records and the administrator or insolvency practice should be able to get access. Its a balls ache but certain carriers will not progress you without proof..in summary the sources are available.