The amateur is exactly correct. If the tire is OK now then it was a portion of tube underneath the bead. The split can appear anywhere, as the tube is not necessarily in the tire with no twists, and may twist as it comes out of the tire. No need to be scared - just carefully push bead inward after mounting to make sure you can't see tire and rim strip is not sitting under the bead. Then inflate partially and check the bead line (some call it witness line) - the raised ridge of rubber running on the tire running just above the edge of the rim. It should be an equal distance from the rim all the way around on both sides. If up, deflate and look for a problem there. If it dives below the rim deflate, spray some mild household cleaner on the area (Fantastic, 409, etc) or use water wth a few drops of of dish soap mixed in, or talc (NOT both wet and dry!). then carefully inflate again, making sure there are not high spots. You will probably have to overinflate (as much as 100psi) and prepare yourself for a POP when the tire seats.