We have seen a similar thing once, where we obtained proteins crystals simply by dehydration of the drop:
Sharpe, M. L., Baker, E. N., and Lott, J. S. (2005) Crystallization of a protein using dehydration without a precipitant. Acta Crystallogr Sect F Struct Biol Cryst Commun 61, 565–568. They diffracted, but weren't much use to us in the end, as they were hard to reproduce or optimise. Hopefully you have more luck than we did!
