> What if they just record you taking the package, follow you home, get a warrant based on probable cause, and search your house and find the package?

If someone sends a package to my house, my taking it into my apartment is evidence of about nothing. Why you would send it somewhere without plausible deniability—say, a PO box you only use for drugs—is beyond me.

Furthermore, they also need to demonstrate you had knowledge of the contents before opening. That's damn hard.