While the dog did have enough oxygen and food to last for 10 days it has since been revealed that Laika died a mere five hours after the launch of Sputnik 2, probably from overheating.
A somewhat moot point because as jonmos points out neither the craft nor Laika were ever intended to be recovered.
For further information: http://www.cnn.com/2002/TECH/space/10/29/russia.dog/index.html