the state sent me the whole ballot, including local races. I suspect they may not even have separate federal-only ballots printed.
I carefully only voted for the federal election
This was my experience as well, bpp3, and I did as you did.
[However it would be difficult to prove I did NOT vote in local races.. maybe next time I should make a copy of the ballot? That wouldn't prove anything since I could always fill it in after..]
Usually the burden of proof falls on the accuser to prove someone is doing wrong. W/r/t state taxation of non-residents this concept is apparently turned on its head. :-ppp