Most all ribs you get at restaurants and even a good majority of the ones they have in grocery stores come in frozen anyway. Like Tip says, you really won't notice any difference so if it is a great deal, especially baby backs which run normal price around here at $3.99, I would buy all they had and ask for more, if it is a good deal.
Practically all meat leaving a packing plant is 'hard-chilled'; meaning it has gone through a nitrogen cooler and it's temperature lowered to 31°-32° F. to maximize keeping it cold during shipping in reefers; so right off the bat it is hard-chilled frozen enough to make it transportable.
I bought something like 30 racks the last time I bought them. They were froze when I bought them and put thme in my freezer and thawed as I needed..I dont mind them myself..I bet the fresh ones are better but I dont mind teh frozen ones..