Poppy I'm not saying that the OP is a bad person. I appreciate that he has made a mistake.
However as an employer I can fully understand why they would no longer want to employ someone who not only accesses confidential info, but then tells other's all about it!
My own view is, the lesson to be learnt here is, DO NOT leave confidential information - to what amounts to (basically laying around) people do snoop, so put in safeguards to protect the company and the staff, I think it is the company who have been naive!.
I have no idea why the OP did what he did, maybe he bragged, panicked and felt telling others lessened the secret - hard to know without being there, and knowing, him!
Maybe the company has lax standards right across the board, and things like this happen often - how do we know?
How the company deals with him, is down to them.
Yes, he did do wrong - he is not a villian - he did not make anything from this, the very opposite in fact.
We, all do silly silly things in our lives, how many times have you said 'if only I could turn the clock back', some people continue doing them, let us hope the OP has learnt from this.
Only the OP knows if this is the first time he has ever done this before.
If yes, then I do not agree he is not to be trusted - maybe take a while to get that back.
If everyone was hung drawn and quarted for silly mistakes there would be no one left walking the streets.
Poppy xx