You should still be able to pitch it and fermentation will most likely start unless you did a huge beer. Or if you have some left over DME make a starter with it to get the yeast woken up.
I never "smack the pack". Not after an episode years ago where the whole pack burst and I ended up with yeast sprayed all over the wall. I always make a starter anyway, so I just pitch the yeast into the starter without smacking it.