What if you go silent, and refuse statements based on constitutional rights? Do they rip the place apart (certainly)? And if the firearms were lost in a boating accident (not found during the search), do you get jailed? Government Nazi's!
That’s why some states require prompt reporting of loss of guns. When they ask “where are they?”, “I lost ‘em” is admission of guilt.
Likewise registering private sales. If they ever find it and its NOT linked to you by a solid paper trail, off to jail.
Instead of going silent, how about saying the three magic words? “Get a warrant.”