When praying on sand, do your feet need to touch the ground directly?

Assalamu alaikum. I was traveling and had to pray outside since I couldn't find a place indoors. The ground was sandy, so I took off my shoes because I wasn't sure if the soles were pure-I had used a portable toilet earlier. To keep clean, I put my jacket down and prayed on it, but during sujood I rested my feet on my shoes to avoid getting sandy. Later, I remembered that your toes should touch the ground during prayer, and I'm worried mine didn't always touch the shoes or the jacket. Does this make my salah invalid?