Mystery flower

These are very beautiful, and quite small. They are not the customary zephyranthes rain lilies, whatever they are. The petals are joined, but are not pointed. They are more in the form, first, of a narrow trumpet, then a bit of a bowl or bell, then semicircular petal edges (everything joined all the way up). They are a bit like a shorter, wider, single freesia blossom. We've seen three so far. They are a sunny, egg-yolk yellow, with red- or pinkish-brown streaks or striped on the back surface (a color similar to Tubergen's species tulips). They are quite short-stemmed and spring up without leaves. We have never seen them before, at least not in our pleasure grounds. Did the birds bring them?