Just listened to the Grieg concerto and it has its good moments and I am pretty sure you can do a lot better than this. So the are a LOT of potential for a really good version.
As you said, you had a memory slip which disturbed you through the rest of the concerto but you came through it pretty well anyway. I've had that many times, especially through my rock/pop careér and even forgot what the number on one of the keyboards (I usually had three) the hammond organ sound was once. That sounded pretty screwed up as it was my solo
. I know how the ice-cold feeling running down your back feels when it suddenly (and always out of nowhere) hits you that you cannot remember what comes next. Second plan? Well, you know the key so here is where your improvising skills comes in