Scott doesn't lock his actual door - he barely closes it. That 'door' opening in his apartment, however, startles the shit out of him because of the havoc it (briefly) wrecks on his sense of spatial awareness.

"Does this look like a storage unit?" He is just kind of sitting on the couch, turned that way and recovering from the spike of adrenaline the abrupt appearance and weird disorientation caused. Not outwardly obvious but racing heart is going on.

But also: "How much stuff, and why?"