Hi H.,
I hate to suggest something that will turn out to be costly, but its not the smell thats the concern and even if the smell is undected, that doesnt mean that the underlying problems are actually gone. You don't want your baby to have any health issues. Getting sick, allergies, asthmas, skin irritations, or anything else because what we cant see isn't really gone.
I just don't think it's worth it, especially if you don't know what kind of mold or mildew it is or why it occured. Even though basements are moist or more humid than the rest of the house, there may have been some kind of wet beyond the usual humidity down there. Some types are sooo much more harmful than the regular bad ones.
I would just buy new.
Good luck
L.