How many hours before the ride did you eat? Beans have carbs, but not all of them are digestible and, in any event, they are slow to digest. So, it's possible that you just ate too late in the day to access the energy you needed for your ride. But I'm no expert. I'm an eat everything in moderation kind of a person.

Putting aside the Paleo idea that if you don't give your body carbs, it will burn fat, it seems to me that you should add in some easily digestible carbs before your long ride days, regardless of whether it's an official cheat day or not. You can still choose vitamin/mineral rich foods instead of just, say, white rice. Why not have something like a banana before your rides (easily digestible, lots of carbs and potassium to boot)? And are you making sure to replace lost electrolytes during and after your rides? For as hot as it's been, it's absolutely imperative that you do.

I like almonds during a ride, but only in addition to something with some easily digestible carbs. Larabars, bananas, and dried apricots are my go-to foods right now during rides.