I have sent myself a car to copy before and a few times the trans, lsd, ect... went back to default settings. The parts were there just the setting weren't. Like I said though, the settings will remain how he tuned it.
I believe that's what's happening. As long as you save and then send the settings should stay. Another question though; can you send a car with three different setups on A B & C and have all three come through or just the one that's selected at the time of sending pasted on all three?
You will only receive the currently selected set-up page.
I have also experienced my tunes mysteriously disappearing while on the truck, so always remember to back up your tunes in a notepad or something similar 👍