That's not carpet. It is either:
1. a layer of mud from when the deuce was in floodwaters during Katrina
2. 2 inches of thick dust from being in a warehouse in Nevada for 30 years
3. a very large paper wasp nest, the wasps are located under the seats, you will find this out when you sit in the truck
4. the accumulation of over 1,000 spiders and their webs, or a web from one VERY LARGE spider
5. the liquified remains of the former driver, who died while driving the truck and the body was left there for many years
Your choice.