He moves around the HQ, you gotta find him
They have full routines, and as Justing is a cook, i would try my luck in the cafeteria kitchen

I have already tried looking for him everywhere and cannot find him, is there anyway i can respawn him?

*he literally does exist*

Just stick around the stairwell, the npcs usually hang around there.

引用自 The Red Builder：

*he literally does exist*

A suggestion: Could you add a dialog to every 3 NPCs like:
Where is …
Then you can select:
… Justin?
… Mark?
… Ivan?
(the one you are asking obviously not in the list)

And then they tell you something like "Hmm, last time I saw him in (second floor, stairways, kitchen, office, …)"

I have searched the whole HQ three times, took breaks for 20min on the stairs in front of the kitchen, the offices and at the entrance, only Ivan and Mark are crossing my way. Any idea on how to conjure Justin again?

Okay, I finally found him, he was stuck in the Boss's office behind the chair

引用自 LausBooB：

Okay, I finally found him, he was stuck in the Boss's office behind the chair

Yeah I think that happened to me, eventually i just exited and re-entered to hq and he came walking out of the boss's room.

引用自 LausBooB：

Okay, I finally found him, he was stuck in the Boss's office behind the chair

you can be happy he was not in the vents… now that they know are safe ;-)