I would use dry shampoo in that scenario. I wash my hair everyday due to sports and also because I just like clean hair. I would be going crazy if I couldn't wash my hair for 4 days. Dry shampoos are great though and I always take some on holidays in case of having to do a lot of travelling between stops. It just keeps the hair fresh and clean smelling.
If I don't wash my hair in a little bit, I still brush it and I would put in dry shampoo, you can find it at almost any store. It is actually beneficial to wash your hair without heat, if you want you could just wash it in the sink or stick your head in the shower. Put it in a messy bun in the meantime if you can't deal, or a ponytail.