The second of these items is the only one I would place any emphasis on. The amount of mail flooding into a congressman's office makes it impossible for the congressman to actually read everything. However, letters from other congressmen most likely receive more attention than from your average Joe.
Now, if his staffers (who actually read most of the mail) didn't notify him of something like this, that isn't good.
However, I do prefer people don't vote when they don't know what they're voting on. The amount of spin is staggering, and if you only know the spin on something, and don't know the facts, voting on it really isn't that honorable... (note that this study really was sleazy)