IPhone 3gs update resulted in lost photos-no warning.

I have a 3gs and did an update today and now all the photos in my phone are gone. No warning was given and I have it set up to back up to my computer, but it did not happen. Is there any way for me to retrieve the photos? Some are exceptionally important (Dad's funeral and burial; pics of parents...) and I would greatly appreciate any help if retrieval is possible.