If you are flying back into the USA from Puerto Rico a passport card will not ...
...have anything to do with it, since Puerto Rico is the US.
So is St Tom, by the way. If anyone gets left on St Tom and calls the office saying "Darn the luck - i'm here without a passport, they won't let me fly back to the States ..." St Tom is the US and passports are not required.
SIG: If you're going to create the drama, at least supply the popcorn.