It's possible that:
* He's a less known actor: His credits may be limited to smaller roles, independent films, or regional productions.
* There's a mix-up in the name: There might be another actor with a similar name who you're thinking of.
* He's not in the public database: He may be a new actor or someone who prefers to keep their work private.
If you can provide more information about Sean Holton or the project you're interested in, it might help to identify him and his work.