Return store.ErrNotFound (#637)
Return store.ErrNotFound (#637)

* Return store.ErrNotFound

* Return errors.NotFound

Co-authored-by: Ben Toogood <73675debcd8a436be48ec22211dcf44fe0df0a64@micro.mu>
Co-authored-by: Asim Aslam <7f7319d555bb84157ce92eea63d39ca4c7bfcbe5@aslam.me>
micro/micro,myodc/micro,micro/micro,micro/micro