How long was the journey?
What was the ratio of water to air?
How many fish were in the bag?
I would not expect the lack of added oxygen to cause fish loss on the journey home (depending on answers to the above questions). After all, the average hobbyist, swapping fish with a mate, does not usually have access to oxygen tanks. I have travelled for 2 days with bagged fish, opening the bag daily to do water changes, and all arrived safe and sound.