Yes, it certainly appears to be infected. Plants are most apt to show symptoms when either the bulb or plant are stressed. Transplanting a bulb from one place to another is stressful to it. If this bulb were given the opportunity to settle in and grow this spring, these symptoms most likely would disappear as growing conditions improved--but the virus is still there. Since your reputable dealer was growing them under ideal conditions, the symptoms were not present and he never knew it. Since this bulb has made contact with other bulbs in the bag, you might want to keep a close eye on the new top growth of those as well throughout the summer.
