I've heard of and experienced something similar, but in opposite circumstances routine, familiar, boring ones. Many years ago, I walked from my house to Hemel Hempstead High Street, in the old town, and suddenly realised, when I got there, that I could remember nothing of my walk since leaving the house. It was mildly alarming. I don't very often go to the old town, but the route to it is very familiar, so no doubt the relative unfamiliarity of my surroundings made me aware of my memory blank up to then.