There are numerous negative hand-prints in cave art with "missing" fingers. For example, this hand print from Gargas Caves; image from http://www.prehistour.eu/carp-guide/gargas-cave-and-nestploria-visitor039s-centre

These were originally interpreted as missing fingers due to frostbite or ritual mutilation. More recent thought is that the painters' fingers were not missing or damaged, just bent over to give the appearance of missing fingers. Some hand-prints show bent-over fingers in profile, so at least some hand-prints were done with bent fingers. Further, the frequency of "missing" fingers is very high compared to modern populations where high rates of frost-bite might be expected.

This was reviewed by Marc Groenen in his 1987 PhD thesis, and published in Groenen, Marc. (1988), "Les représentations de mains négatives dans les grottes de Gargas et de Tibiran (Hautes-Pyrénées). Approche méthodologique", Bulletin de la Société royale belge d'Anthropologie et de Préhistoire 99, 81-113: https://www.researchgate.net/publication/290086725_Les_representations_de_mains_negatives_dans_les_grottes_de_Gargas_et_de_Tibiran_Hautes-Pyrenees_Approche_methodologique

Also, see R. Dale Guthrie, The Nature of Paleolithic Art, University of Chicago Press, 2005. The publisher has a blog post discussing the discussion of this issue in this book: http://pressblog.uchicago.edu/2006/02/27/paleolithic-handprints.html