Just taught slap dance to my sims and the memento isn't filling. Same goes with eating the local meals. Their actual memories say that they've learned slap dance, just nothing in the vacation mementos pops up?
With local dances, it’s like with local greetings, you need to do them a couple of times before your sim will actually learn to do them properly – and then you’ll get memento. You can continue learning at home – just switch on music and dance.

And for eating local meals, you need to let your sim finish to eat it (don’t cancel action before), also there is only 1 of 3 meals in each location that fulfills memento, so maybe you tried the wrong one.