Myriam, I grow several Hippeastrum, but not H. papilio, so I can't say for certain. I do grow some that do not go dormant though, and they have gone through periods when the leaves have yellowed and the plants appeared to go dormant. During that time I did give them only a little water, but would say I kept them on the dry side. When they started sending up new leaves I started watering regularly. I would recommend that you do the same- if the bulb looks healthy and there are no leaves, the need for water is minimal. Those I grow that do go dormant seem to keep fleshy roots year round, so I believe yours will also keep white, firm roots.
Those I grow that go dormant are kept completely dry during dormancy. They start sprouting on their own, and that's what lets me know to start watering them.
Best of luck!
