Did he just lie and say he wasn't working at those places? Or did the question never come up?

When I used to interview I always had to check a box that said I wasn't currently employed, or they would ask at some point.

funny thing was he had other places on his linkedin under "active employment" but we never really dug into it (until we learned he was full-time there) because he just seemed like the kind of person who wouldn't keep his LinkedIn up to date.