Fording a river at night is fairly stupid to begin with. No amount of gear will make up for stupid.
Given the fact that you choose to stay in place, rather than just returning to your car. You don't really need a fishing kit, you have a snickers, remember. Even without a food source you could more than likely make it back to your car without it. I would probably only include the snickers for morale.
I like the possibles pouch idea from bushcraft. I keep two contractor bags and two heavy duty mylar heat sheets it there. There you have ground insulation with one of the contractor bags, the other can act as a sleeping bag. And you can construct a pretty sturdy shelter from the heat sheets.
A knife and a fire kit is a must. My knife is attached to my belt by a small carabiner so it won't fall out. In the fire kit I keep various types of tender, cotton balls, wet fire, tender quik. I also have waterproof matches in a small waterproof bag, and a bic lighter wrapped in ranger bands (cut up bike inner tubes) in a separate waterproof bag. I know people that also keep ferrous rods in their kit, I don't because I find them inadequate under stressful conditions. I've been camping and hiking for 20 years and I've never had a bid fail to light. Its also pretty simple to light a lighter.
I would also throw a decent compass and a whistle in there. If you planned properly and oriented yourself, you should be able to find the general location of your vehicle or the road from basic bearings.
A collapsible water bottle with an emergency filter or straw should be able to take up little space as well. Barring that, just drink from the river you fell into. Worst case you get diarrhea, which isn't a very big problem in a short term scenario like this. You can even throw a few tablets of immodium in your pouch to counteract that.
I would also add a PLB, as that would probably be your most important piece of gear. It should be dummy corded and tethered to you with no chance of getting lost. Its the one piece of gear that would eliminate the need for everything else. Especially if you are unable to rescue yourself or your injured.