How cold does it get on your porch? I looked up your winter temperatures for Reno, and you have the potential for frost from November through March. So if your porch isn't heated, it just may be a little too cold to overwinter Amaryllis. An unheated shed could have the same problem. If the basal plate of the bulb freezes, it will die. Also, how wet was the soil? Too wet during the winter, and the bulbs could rot. There are so many variables. The pots themselves shouldn't have been the issue. The standard procedure is to either let the Amaryllis grow all winter in doors or force the Amaryllis to go dormant in the winter (replicating the "in the wild" dormancy of native Amaryllis). You can let the Amaryllis dry out in the pot, cut off the wilted leaves and store the pot in a cool dry dark place, above freezing for a minimum of 8- 10 weeks. Some people take the bulb out of the pot and store that over the winter. That actually insures that the bulb is totally dry. A basement or an unheated closet are the best locations. The only other suggestion would be to treat the plants, on the porch, the same way you treat the ones you have indoors. Bring them inside if frost is expected and cover them with a frost cover when the temperatures are below 40. You can try this (its a lot of work!) and see if you are able to get the bulbs through the winter. You would definitely have to reduce watering with the colder soil.
The microclimate at your Mom's may keep the bulbs from freezing. Bulbs planted right against a wall can get some warmth off the wall at night. Sometimes coastal locations can stay a few degrees warmer than inland, enough that the Amaryllis will come through the winter without freezing, esp. if they are mulched and not kept too wet. I know that some gardeners are successful in growing Amaryllis outdoors in North Carolina. Some of the "pass along" cultivars, also Red Lion and Apple Blossom, seem to be a little bit hardier outdoors.
