I'm one of the rare people that collects credit card receipts at the point of sale, but I take a photo of the gas pump if the printer doesn't work. Every paper (and photo) receipt goes into my tracking application, usually every week or two. When the bill comes, I use the app by entering the ending balance, and ticking off each item.
DW had one yesterday where she was exactly $27 off. I said look for a transposed pair of digits, but she didn't find one. You might be looking through 20 or 30 transactions and miss the $769.37 should have been $796.37.