Lilies are full sun plants. Can you plant it in the ground?

Could be too much moisture.

Lilies are not houseplants. While they may be sold potted and in bloom for seasonal displays (usually around a holiday like Easter or Mother's Day), that should be a very temporary situation and they really need to be planted outside for best results.

btw, lily flowers do not last very long, especially under indoor conditions. If they lasted a week, I'd consider myself lucky.