If the company went through bankruptcy after he purchased the shares and was subsequently re-capitalized and then became successful, his shares would have been canceled in the recapitalization. Likely by dilution to minutia.

Regardless of the method, the company would be required to inform all shareholders of such events. I'd be curious to know how the corporate books were managed at the time he purchased the shares.

He can write it off as a total loss.

Some companies do a reverse split just before liquidity event to wipe out former employees and lock-in current employees, like a 10:1 reverse split.