The 3rd Pilot is not missing, It's episode 16.
1. Pilot: The jet Assisted Take off Chevy (Episode6)
2. Pilot: The Vacuum Toilet (Episode11)
3. Pilot: Larrys lawn chair Ballon episode. (Episode16)
Compared to the Mythbuster episode list on Wikipedia, many episodes are not in Broadcasting order on the DVDs. Same Problem on the other Season DVDs
But there are many Episodes missing on the other Seasons DVDs, mostly Special Episodes.
27 Episodes are missing on the DVDs so far from Season 2 to Season 8. Season 1 is the only complete Season on DVD.