Waiting to be punished

Hello. I am an LP, I've been with the company for almost a year.

I had an NRI (non-recovery incident) I was involved in almost 2 months ago. I am told that I will be written up for it soon, and that I cannot make apprehensions in the mean time. I see the disappointed looks on everyone's faces when I dont catch someone who we all know is stealing, but I don't want to tell them I can't do the one job I am paid to do.

My question: how long is too long? When I worked for Target, any time they didn't reprimand you within a month it would be dropped because they did not act in a reasonable amount of time. And, I'm on a final for 6 months- from the day I get my written?

I keep getting told that I will be written up soon. But now, I'm going to be punished for 8 months when it should only be 6?