A diploid daylily can be coverted to a tetraploid daylily to double its number of chromosomes so that it can then be crossed with another tetraploid, but it's not something the average person would typically do. It isn't easy and requires the use of certain chemicals with no guarantee of success. You could look to see if your preferred diploid has already been converted by someone. As far as the one you bid on, if one parent was a converted diploid it should have said so, the formerly dip parent's name being prefixed by tet or tetra. Do you know the names of the parents of your dip x tet?