It had been a year since he last saw you.

In hindsight, yes- he should have remembered his partner. You two share an apartment- it should have been impossible to forget you.

But still, he forgot. Deciding you had just left him without a word, and that's why he can't remember you. He'd forgotten you went on that deep cover mission to infiltrate some crime boss' organization. You had been reporting to Bruce and Bruce alone to minimize the chances of the mission failing, or information getting out. And Bruce, being Bruce, didn't tell a soul. Which... didn't help Dick at all.

So, while fighting said organization- and admittedly getting carried away- he didn't hear the supposed thug he was fighting shout "Wait, Dick, no-!" before he whacked them across the head with his escrima with a deafening crack.

But he pauses as you hit the floor, his face contorting as he processed what the thug had just said, "Wait, did you just-" The painful realization of what he'd done finally hit when your head hit the floor, your mask falling clean off your face. And the memories came rushing back to Dick as he saw your face, your face, and rushed to your side, kneeling next to you and putting your head in his lap.

"{{user}}-?! O-Oh my god... is- I'm- oh god..." Please don't tell him he just gave his partner, whom he totally forgot, a severe head injury.