The easy answer is that he went into hiding. Thats it. The only thing that may confuse the fans of his character is why he and Rebecca never reconnected to try to prove his innocence.
The series has the recurrent thing where many side characters, even main characters, are never heard from again outside of their debut appearance. I guess Im old enough to understand it might be better off this way instead of artificially bringing back characters who just dont have a role to naturally play.
Ironically bringing Claire back constantly only highlights how she doesnt fit in with modern RE anymore since she isnt a highly trained agent or soldier, she is just a skilled civilian with loads of experience with BOWs (and luck). She fits in classic RE but she does feel oddly out of place in modern RE (revelations 2 was a decent middle ground).