I can relate, I know that when I found things (usually I was snooping though, I didn't just stumble across it) it was very difficult not to confront. Most of us in the thick of our sitches get spinning when we find evidence of the OP. You're right, it wasn't the right way to approach it from a DBing standpoint, but very few people can control their emotions enough to just keep on DBing. Detachment is about the not emotionally reacting, but detachment is not a switch you throw on and suddenly you're detached. It is a process that takes time and effort to finally arrive at a high enough level to remain even through incidents like this.
I say all that to say don't beat yourself up too much. The problem with confrontation is that it rarely goes the way you would like it to. But water under the bridge, just keep working and focusing on you! Better days are ahead.
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018