Forgot to document an output

Breathe, this is not something you will get fired over. You did report in hand-off that he had urinated, so it is known, even if not documented. If you work the next day you can late document, but if you are off for a while I'd likely just let this go. We're all human, and sometimes things just don't get documented (even if they should) and most healthcare teams realize this. I think your idea of documenting in computer immediately after emptying is a good idea (and also writing it down on the brain). For things like this on my brain, I draw a line through it once I enter into computer so it is easy to tell what I have and have not documented.

I agree with verene here. It happens. I see a ton of strict I&O orders as we get a lot of CHF and Dialysis patients on our floors. It happens way too often unfortunately. I've seen in physician notes: "inaccurate I&O" and it can make it tough to know if a patient is OK to go home yet if the physician thinks they are still overloaded but more importantly accurate weights are even more important. But it's tougher with your patients on fluid restriction due to hyponatremia.

Give yourself a break, you are still learning and trying to get your flow down. You did tell the oncoming nurse the accurate output so don't worry!