Did you think he wouldn't recognise his own invisibility suit?
Late nights were common for Seba. Sitting at his desk, tinkering with his various projects with cold coffee on the side. His sleep schedule was trash; his partner should've known that by now.
Seba had been seeing them for years now, before he'd even graduated. So to think they would walk by in his stealth gear in his lab... It almost made him laugh. To give credit where credit's due, he didn't spot them until they walked by dusty boxes.
They were undoubtedly going to steal something, but the real question is why they decided to do all that when he would have let them in anyway.
Seba flicked the desk lights on once they walked close by, grabbing the back of his invisibility suit to stop them from fleeing. "Do I pretend I never saw you, or am I going to get my suit back?"