Visible crew/equipment: When Dana arrives at the Ghostbusters' office, a crew member can be seen moving behind the filing cabinets behind where Janine is sitting. It could be Venkman, but even after Venkman walks over to Dana, there's still a rogue hand there, showing us it wasn't Venkman and was a crew member. (00:22:10)
Chosen answer: Thor sounds nothing like "thaw" (at least, not with Jane's accent). Also, "Thor" is not an uncommon name in Scandanavian countries, and even if she didn't assume he was from there, she probably just thought it was an odd name and left it at that.
Xofer