By that stage England were trailing 12-3 but two Alex Cuthbert tries, and eight points from Dan Biggar, saw Wales romp to a 30-3 win, their record victory over their old rivals.
And Hartley, who started for England against France and came off the bench in their other four matches, revealed that while Stuart Lancaster's side did not take Wales lightly, they did not expect such a heavy defeat.
"The momentum Wales gained was huge and it's disappointing to lose in that fashion. No-one saw that happening," said Hartley.
"We were full of respect for Wales and we know what they can do but we didn't think it'd be as one-sided as that.
"It [the Six Nations] ended on a bit of a sour note for us so there's a bad taste in the mouth there.
"But we can get back on track because we've come a long way."