What symptoms did the lilies show? Was it an experienced bulb person who diagnosed?

Easter lilies are listed as being hardy down to zone 4.

Easter lilies, Lilium longiflorum, are very prone to a virus that is transmitted by aphids. This is what has the potential to infect your other lilies. It is just best to keep these types of lilies in a separate part of your garden. And be on the look out for aphids. The bulbs will come back but will not be blooming at Easter in future years :-)

thank you.