What could cause the fin antenna to fall/snap off but not affect the roof rack?

[dmaxdmax]

We're looking at a used 2013 RX350 and where the antenna should be is a patch of tape. It's at a Lexus dealer who says that it will be replaced by early next week and he has no idea how it happened. What could cause that? The roof rails and crossbars are unscathed and we didn't see scratches on the hatch, though we didn't climb up to look at the roof.

 

[Lexucator]

If there is no residual damage, such as scratches around the area where an antennae should reside, it could have simply been stolen while the car sat on the lot.