In what situation would it make sense for fine-mapping a region of the associated SNP

Question

[wondereye]

Lets say that in an original GWAS study you find a SNP in gene to be associated with your trait of interest. You then preform a follow up study using the original sample used in the original GWAS but this study is using a different phenotype that is similar to the phenotype in the original GWAS study. The only associations found in the follow up study were from in the sample of original GWAS study. What conclusions can one draw from this? Does this constitutes the region as a candidate for fine-mapping?