Betcha you didn't declare the leftovers
I am a frequent border crosser myself, both on the Cascades and in my own car. The inspection process on the Cascades is much more similar to an airport inspection than crossing in a car and can be more intrusive/intense than the officer at the booth at a highway crossing generally is. If you are carrying a bag of take out, you will be told to toss it.
Personally, I don't push the food rules at all (which are the same for any mode). The details are quite complex should you want to get into them (avocados are apparently okay, oranges are not), but a simple rule of thumb is packaged products are okay except meat, not commercially packaged, no.
I am a NEXUS member, and NEXUS members are expected to know and abide by ALL the rules without being asked or prompted. That is the "trust" part of "trusted traveler". I am anxious to protect my NEXUS card, it is just too damned handy. There are few quicker ways to have a NEXUS membership revoked than to violate the food/ag rules.
When in doubt, declare.