I am sorry for your loss. I do not believe a long walk would cause an early miscarriage. In fact, people who are pregnant without IVF often exercise to their hearts content without experiencing issues.
I specifically asked a doctor about the fragrance issue. It will not cause a miscarriage. The only time it could be harmful to embryos is prior to the time they are transferred back to you. Once that is done, fragrances will not cause any harm.
I know it is hard not to question everything in this type of situation. I'm still doing it as a result of an ectopic in January, but really, I this is probably a situation that was out of your control. There is most likely absolutely nothing that you could have done that would have made a difference.