i'm not entirely sure but i believe you have to buy the crown race that comes with the headset. its a interference fit on the fork so if you pulled the fork its probably still there. yes tapered fork is 1 1/2 on the crown race part. if you can see on this one the little metal ring should be there on top of the fork crown. if that makes sense to ya. it would be uncommon for the crown race to just fall off. I am betting its still there but maybe the stem was not correctly torqued down. the little button at the top doesnt need to be super tight the bolts around the steerer tube on the sides have to be torqued to spec probably around 9 newton meters.