Potted Lilies are treated with chemicals to suppress growing (shorter Lilies easier to store and sell). Also, the bulb could be small. Next year it'll be fine. Do not cut the foliage until it will go dry and brown.

Have you had a lot of rain? I have a lot of established lilies, and some of my orientals, notably the Stargazers, are unusually short. I do have some that are only four inches to a foot, with a single bud. Since for me nothing has changed, I am wondering if somehow all the rain is responsible. It would be interesting to know if other people are having this problem. I have much fewer buds on all the lilies this year, with the exception of my Orienpets.